Sifting through countless of stocks in the Insurance industry can be tedious, and sometimes two stocks are just too similar to judge which is the better investment. If you’re on the fence about investing in Arthur J. Gallagher & Co. or Aon plc because you’re not sure how they measure up, it’s important to compare them on a few factors before making your decision.

Read on to learn how Arthur J. Gallagher & Co. and Aon plc compare based on key financial metrics to determine which better meets your investment needs.

About Arthur J. Gallagher & Co. and Aon plc

Arthur J. Gallagher & Co., together with its subsidiaries, provides insurance and reinsurance brokerage, consulting, and third-party property/casualty claims settlement and administration services to entities and individuals worldwide. The company operates in Brokerage and Risk Management segments. Its Brokerage segment offers retail and wholesale insurance and reinsurance brokerage services; assists retail brokers and other non-affiliated brokers in the placement of specialized and hard-to-place insurance; and acts as a brokerage wholesaler, managing general agent, and managing general underwriter for distributing specialized insurance coverages to underwriting enterprises. This segment performs activities, including marketing, underwriting, issuing policies, collecting premiums, appointing and supervising other agents, paying claims, and negotiating reinsurance; and offers services in the areas of insurance and reinsurance placement, risk of loss management, and management of employer sponsored benefit programs. The Risk Management segment provides contract claim settlement and administration services; and claims management, loss control consulting, and insurance property appraisal services. The company offers its services through a network of correspondent brokers and consultants. It serves commercial, industrial, public, religious, and nonprofit entities, as well as underwriting enterprises. The company was founded in 1927 and is headquartered in Rolling Meadows, Illinois.

Aon plc operates as a professional services firm in the United States, rest of the Americas, the United Kingdom, Ireland, rest of Europe, the Middle East, Africa, and the Asia Pacific. It operates through Risk Capital and Human Capital segments. The company offers commercial risk solutions comprising retail and insurance brokerage, specialty solutions, global risk consulting, captives management, and affinity programs; health solutions, such as consulting and brokerage, consumer benefits, and talent advisory services; and wealth solutions, including retirement consulting and investments. It also provides treaty and facultative reinsurance; strategy and technology group solutions; insurance-linked securities, capital raising, strategic advice, restructuring, and merger and acquisition services; and risk management products and solutions, capital market solutions, and corporate finance advisory services. In addition, the company offers strategic design advice and actuarial services; pension risk transfer and integrated pension administration; and investment advisory services on developing and maintaining investment programs across various plan types, including defined benefit plans, defined contribution plans, master trusts, and pooled employer plans for corporations, public pensions, endowments, and foundations. Aon plc was incorporated in 1979 and is headquartered in Dublin, Ireland.

Latest Insurance and Arthur J. Gallagher & Co., Aon plc Stock News

As of April 17, 2026, Arthur J. Gallagher & Co. had a $56.9 billion market capitalization, compared to the Insurance median of $5.4 million. Arthur J. Gallagher & Co.’s stock is NA in 2026, NA in the previous five trading days and down 33.96% in the past year.

Currently, Arthur J. Gallagher & Co.’s price-earnings ratio is 38.6. Arthur J. Gallagher & Co.’s trailing 12-month revenue is $13.0 billion with a 11.5% net profit margin. Year-over-year quarterly sales growth most recently was 36.7%. Analysts expect adjusted earnings to reach $13.214 per share for the current fiscal year. Arthur J. Gallagher & Co. currently has a 1.3% dividend yield.

Currently, Aon plc’s price-earnings ratio is 19.5. Aon plc’s trailing 12-month revenue is $17.2 billion with a 21.5% net profit margin. Year-over-year quarterly sales growth most recently was 3.7%. Analysts expect adjusted earnings to reach $18.987 per share for the current fiscal year. Aon plc currently has a 0.9% dividend yield.

How We Compare Arthur J. Gallagher & Co. and Aon plc Stock Grades

Stock evaluation requires access to huge amounts of data and the knowledge and time to sift through it all, make sense of financial ratios, read income statements and analyze recent stock movements. AAII created A+ Investor, a robust data suite that condenses data research in an actionable and customizable way suitable for investors of all knowledge levels, to help investors streamline and work through such data.

AAII’s proprietary stock grades come with A+ Investor. These offer intuitive A‐F grades for each of five key investing factors: value, growth, momentum, earnings estimate revisions and quality. Here, we’ll take a closer look at Arthur J. Gallagher & Co. and Aon plc’s stock grades to see how they measure up against one another.

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Arthur J. Gallagher & Co. and Aon plc Stock Value Grades

Company	Ticker	Value
Arthur J. Gallagher & Co.	AJG	F
Aon plc	AON	D

Successful stock investing involves buying low and selling high, so stock valuation is an important consideration for stock selection.

Buying stocks that are going to go up typically means buying stocks that are undervalued in the first place, although momentum investors may argue that point.

AAII’s A+ Investor Value Grade derives from a stock’s value score. The Value Score is the percentile rank of the average of the percentile ranks of the price-to-sales ratio, price-earnings ratio, enterprise-value-to-EBITDA (EV/EBITDA) ratio, shareholder yield, price-to-book-value ratio and price-to-free-cash-flow ratio. The score is variable, meaning it can consider all six ratios or, should any of the six ratios not be valid, the remaining ratios that are valid. To be assigned a Value Score, stocks must have a valid (non-null) ratio and corresponding ranking for at least two of the six valuation ratios.

Stocks with a Value Score from 81 to 100 are considered deep value, those with a score between 61 and 80 are a good value and so on.

Arthur J. Gallagher & Co. has a Value Score of 14, which is Ultra Expensive. Aon plc has a Value Score of 30, which is Expensive.

The Value Stock Winner: No Clear Winner

Neither Arthur J. Gallagher & Co. or Aon plc has a high enough value grade to be considered a “winner.” Investors who are considering these companies should do additional due diligence and research to see if either could be a good addition to their portfolio. It’s important to look at a wide range of financial metrics in order to determine if Arthur J. Gallagher & Co. or Aon plc is the better investment when it comes to value.

Arthur J. Gallagher & Co. and Aon plc Growth Grades

Company	Ticker	Growth
Arthur J. Gallagher & Co.	AJG	A
Aon plc	AON	A

The foundation of growth investing is seeking out stocks of companies exhibiting strong, consistent and prolonged growth that is expected to continue into the future.

In order to compute the growth score and assign it a letter grade, the percentile ranks for each of three components‐consistency of annual sales growth, five-year sales growth rankings adjusted for extreme levels, and consistency of positive annual cash from operations‐must be determined. These three rank figures are added together, and the sum is ranked against the entire stock universe to arrive at a company’s Growth Score to create an equal distribution of grades.

The companies in the bottom 20% of the stock universe receive Growth Grades of F, considered to be very weak, while those in the top 20% receive A grades, which are considered very strong.

Arthur J. Gallagher & Co. has a Growth Score of 89, which is Very Strong. Aon plc has a Growth Score of 100, which is Very Strong.

The Growth Grade Winner: It’s a Tie!

Looking at the Growth Grade breakdown above, both Arthur J. Gallagher & Co. and Aon plc have a grade of A. For investors who focus solely on a company’s upward growth, further research should be conducted into both companies’ other financial metrics before deciding whether to invest.

Arthur J. Gallagher & Co. and Aon plc’s Estimate Revisions Grades

Company	Ticker	Earnings Estimate
Arthur J. Gallagher & Co.	AJG	D
Aon plc	AON	C

Earnings estimate revisions scores consider the magnitude of a company’s earnings surprise in its last two reported fiscal quarters. Often, positive surprises beget further positive surprises‐or at least continued sales growth (the exact opposite is generally true, too).

Estimate revisions offer an indication of what analysts are thinking about the short-term prospects of a firm. Estimate revisions are based on the statistical significance of a firm’s last two quarterly earnings surprises and the percentage change in its consensus estimate for the current fiscal year over the past month and past three months.

Arthur J. Gallagher & Co. has a Earnings Estimate Score of 32, which is Negative. Aon plc has a Earnings Estimate Score of 49, which is Neutral.

The Earnings Estimate Revisions Stock Winner: No Clear Winner

Neither Arthur J. Gallagher & Co. or Aon plc has an Earnings Estimate Revisions Grade that could be considered a “winner.” Investors considering these companies should do additional due diligence and research to see if either could be a good addition to their portfolios. It’s important to look at a wide range of financial metrics in order to determine if Arthur J. Gallagher & Co. or Aon plc is the better investment when it comes to estimate revisions.

Other Arthur J. Gallagher & Co. and Aon plc Grades

In addition to Value, Estimate Revisions and Growth, A+ Investor also provides grades for Momentum and Quality.

Momentum grades help uncover stocks experiencing anomalously high rates of return; research finds that stocks with high relative levels of momentum tend to outperform, whereas those with low levels of momentum tend to continue underperforming.

AAII’s A+ Investor Quality Grade comes from the ranking of key metrics. Specifically, the quality grade is the percentile rank of the composite of return on assets (ROA), return on invested capital (ROIC), gross profit relative to assets, buyback yield, change in total liabilities to assets, accruals, Z double prime bankruptcy risk (Z) score and F-Score.

These 2 key factors, when combined with the above, provide a holistic view into a particular stock. Further, by joining A+ Investor you can see whether Arthur J. Gallagher & Co. and Aon plc pass any of our 60+ stock screens that have outperformed the market since their creation.

So, Which Is the Better Investment, Arthur J. Gallagher & Co. or Aon plc Stock?

Overall, Arthur J. Gallagher & Co. stock has a Value Score of 14, Growth Score of 89 and Estimate Revisions Score of 32.

Aon plc stock has a Value Score of 30, Growth Score of 100 and Estimate Revisions Score of 49.

Comparing Arthur J. Gallagher & Co. and Aon plc’s grades, scores and metrics can act as a solid basis to determine whether they may be a good investment or not. You’ll also want to look at your portfolio’s asset allocation as well as your risk tolerance and financial goals to see if either of these stocks would make a good fit for you. AAII can help you figure out which investments align with your individual needs and preferences.

Investors are encouraged to do their own due diligence and research. In this way, individuals can effectively become managers of their own assets‐without having to rely on others for financial independence. You can count on AAII for timeless articles on financial planning and stock-picking, unbiased research and actionable analysis.

A+ Investor adds to our qualitative teaching with a powerful data suite to help you whittle down investment choices to find stocks, exchange-traded funds (ETFs) or mutual funds that meet your needs.

AAII Disclaimer

We make no representations or warranties that any investor will, or is likely to, achieve profits similar to those shown, because past, hypothetical or simulated performance is not necessarily indicative of future results. Before making an investment decision, you should consider your circumstances and whether the information on our content is applicable to your situation. This information was prepared in good faith, and we accept no liability for any errors or omissions. The full disclaimer can be read here.