Investors interested in stocks from the REIT and Equity Trust - Retail sector have probably already heard of American Assets Trust (AAT) and Realty Income Corp. (O). But which of these two stocks presents investors with the better value opportunity right now? Let's take a closer look.The best way to find great value stocks is to pair a strong Zacks Rank with an impressive grade in the Value category of our Style Scores system. The Zacks Rank is a proven strategy that targets companies with positive earnings estimate revision trends, while our Style Scores work to grade companies based on specific traits.American Assets Trust and Realty Income Corp. are sporting Zacks Ranks of #2 (Buy) and #3 (Hold), respectively, right now. Investors should feel comfortable knowing that AAT likely has seen a stronger improvement to its earnings outlook than O has recently. But this is just one factor that value investors are interested in.Value investors analyze a variety of traditional, tried-and-true metrics to help find companies that they believe are undervalued at their current share price levels.Our Value category grades stocks based on a number of key metrics, including the tried-and-true P/E ratio, the P/S ratio, earnings yield, and cash flow per share, as well as a variety of other fundamentals that value investors frequently use.AAT currently has a forward P/E ratio of 12.51, while O has a forward P/E of 16.67. We also note that AAT has a PEG ratio of 1.56. This popular metric is similar to the widely-known P/E ratio, with the difference being that the PEG ratio also takes into account the company's expected earnings growth rate. O currently has a PEG ratio of 5.24.Another notable valuation metric for AAT is its P/B ratio of 1.43. Investors use the P/B ratio to look at a stock's market value versus its book value, which is defined as total assets minus total liabilities. By comparison, O has a P/B of 1.51.These are just a few of the metrics contributing to AAT's Value grade of B and O's Value grade of D.AAT has seen stronger estimate revision activity and sports more attractive valuation metrics than O, so it seems like value investors will conclude that AAT is the superior option right now. Zacks Names "Single Best Pick to Double" From thousands of stocks, 5 Zacks experts each have chosen their favorite to skyrocket +100% or more in months to come. From those 5, Director of Research Sheraz Mian hand-picks one to have the most explosive upside of all. It’s a little-known chemical company that’s up 65% over last year, yet still dirt cheap. With unrelenting demand, soaring 2022 earnings estimates, and $1.5 billion for repurchasing shares, retail investors could jump in at any time. This company could rival or surpass other recent Zacks’ Stocks Set to Double like Boston Beer Company which shot up +143.0% in little more than 9 months and NVIDIA which boomed +175.9% in one year.Free: See Our Top Stock and 4 Runners Up >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report American Assets Trust, Inc. (AAT): Free Stock Analysis Report Realty Income Corporation (O): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research