Sifting through countless of stocks in the Specialized REITs 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 American Tower Corporation or Iron Mountain Incorporated 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 American Tower Corporation and Iron Mountain Incorporated compare based on key financial metrics to determine which better meets your investment needs.

About American Tower Corporation and Iron Mountain Incorporated

American Tower Corporation one of the largest global REITs, is a leading independent owner, operator and developer of multitenant communications real estate with a portfolio of over 148,000 communications sites and a highly interconnected footprint of U.S. data center facilities. American Tower Corporation was incorporated in 1995 in Delaware and is based in Massachusetts, Boston.

Iron Mountain Incorporated is trusted by more than 240,000 customers in 61 countries, including approximately 95% of the Fortune 1000, to help unlock value and intelligence from their assets through services that transcend the physical and digital worlds. Our broad range of solutions address their information management, digital transformation, information security, data center and asset lifecycle management needs. Iron Mountain Incorporated is based in Portsmouth, New Hampshire. Iron Mountain Incorporated was founded in 1951 and is incorporated in Delaware and is based in Portsmouth, New Hampshire.

Latest Specialized REITs and American Tower Corporation, Iron Mountain Incorporated Stock News

As of September 4, 2026, American Tower Corporation had a $81.9 billion market capitalization, compared to the Specialized REITs median of $7.5 million. American Tower Corporation’s stock is up 0.2% in 2026, down 0.2% in the previous five trading days and down 9.86% in the past year.

Currently, American Tower Corporation’s price-earnings ratio is 24.2. American Tower Corporation’s trailing 12-month revenue is $10.9 billion with a 31.1% net profit margin. Year-over-year quarterly sales growth most recently was 4.7%. Analysts expect adjusted earnings to reach $6.984 per share for the current fiscal year. American Tower Corporation currently has a 4.1% dividend yield.

As of September 4, 2026, Iron Mountain Incorporated had a $34.8 billion market cap, putting it in the 91st percentile of all stocks. Iron Mountain Incorporated’s stock is up 40.9% in 2026, down 0.5% in the previous five trading days and up 28.31% in the past year.

Currently, Iron Mountain Incorporated’s price-earnings ratio is 83.3. Iron Mountain Incorporated’s trailing 12-month revenue is $7.6 billion with a 5.5% net profit margin. Year-over-year quarterly sales growth most recently was 18.5%. Analysts expect adjusted earnings to reach $2.481 per share for the current fiscal year. Iron Mountain Incorporated currently has a 3.0% dividend yield.

How We Compare American Tower Corporation and Iron Mountain Incorporated 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 American Tower Corporation and Iron Mountain Incorporated’s stock grades to see how they measure up against one another.

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American Tower Corporation and Iron Mountain Incorporated Growth Grades

Company	Ticker	Growth
American Tower Corporation	AMT	A
Iron Mountain Incorporated	IRM	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.

American Tower Corporation has a Growth Score of 100, which is Very Strong. Iron Mountain Incorporated has a Growth Score of 89, which is Very Strong.

The Growth Grade Winner: It’s a Tie!

Looking at the Growth Grade breakdown above, both American Tower Corporation and Iron Mountain Incorporated 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.

American Tower Corporation and Iron Mountain Incorporated’s Quality Grades

Company	Ticker	Quality
American Tower Corporation	AMT	B
Iron Mountain Incorporated	IRM	C

Like the Value Grade, AAII’s A+ Investor Quality Grade comes from the percentile rank of key metrics. Specifically, the Quality Score is the percentile rank of the average of the percentile ranks 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 the F-Score.

The score is variable, meaning it can consider all eight measures or, should any of the eight measures not be valid, the remaining measures that are valid. To be assigned a Quality Score, stocks must have a valid (non-null) measure and corresponding ranking for at least four of the eight quality measures.

The Quality Score is used to assess the underlying “quality” of a particular stock. A higher-quality stock possesses traits associated with upside potential and reduced downside risk. Backtesting of the Quality Grade shows that stocks with higher grades, on average, outperformed stocks with lower grades over the period of 1998 through 2019.

Stocks receive better grades (higher scores) for having higher scores for the quality subcomponents and worse grades (lower scores) for lower scores for the subcomponents.

American Tower Corporation has a Quality Score of 78, which is Strong. Iron Mountain Incorporated has a Quality Score of 52, which is Average.

The Quality Grade Winner: American Tower Corporation

As you can clearly see from the Quality Grade breakdown above, American Tower Corporation has a better overall quality grade than Iron Mountain Incorporated. For investors who are looking for companies with higher quality than others in the same industry, American Tower Corporation could be a good stock to add to their portfolios. However, it’s important for investors to analyze multiple factors based on a wide range of metrics before deciding whether to buy.

American Tower Corporation and Iron Mountain Incorporated’s Momentum Grades

Company	Ticker	Momentum
American Tower Corporation	AMT	D
Iron Mountain Incorporated	IRM	C

Momentum grades help to 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. Momentum is based on the price change of a stock over a specified period relative to all other stocks.

Typically, AAII looks at the weighted relative strength over the trailing four quarters. The weighted four-quarter relative strength rank is the relative price change for each of the past four quarters. The most recent quarterly price change is given a weight of 40% and each of the three previous quarters are given a weighting of 20%.

American Tower Corporation has a Momentum Score of 28, which is Weak. Iron Mountain Incorporated has a Momentum Score of 54, which is Average.

The Momentum Stock Winner: No Clear Winner

Neither American Tower Corporation or Iron Mountain Incorporated has a strong enough Momentum Grade to 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 American Tower Corporation or Iron Mountain Incorporated is the better investment when it comes to momentum.

Other American Tower Corporation and Iron Mountain Incorporated Grades

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

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

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.

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 American Tower Corporation and Iron Mountain Incorporated pass any of our 60+ stock screens that have outperformed the market since their creation.

So, Which Is the Better Investment, American Tower Corporation or Iron Mountain Incorporated Stock?

Overall, American Tower Corporation stock has a Growth Score of 100, Momentum Score of 28 and Quality Score of 78.

Iron Mountain Incorporated stock has a Growth Score of 89, Momentum Score of 54 and Quality Score of 52.

Comparing American Tower Corporation and Iron Mountain Incorporated’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.