Investors with an interest in Financial - Investment Management stocks have likely encountered both Atlas (ATCO) and BlackRock (BLK). But which of these two companies is the best option for those looking for undervalued stocks? Let's take a closer look.Everyone has their own methods for finding great value opportunities, but our model includes pairing an impressive grade in the Value category of our Style Scores system with a strong Zacks Rank. 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.Atlas and BlackRock are sporting Zacks Ranks of #1 (Strong Buy) and #3 (Hold), respectively, right now. This system places an emphasis on companies that have seen positive earnings estimate revisions, so investors should feel comfortable knowing that ATCO is likely seeing its earnings outlook improve to a greater extent. But this is just one piece of the puzzle for value investors.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.ATCO currently has a forward P/E ratio of 9.58, while BLK has a forward P/E of 21.65. We also note that ATCO has a PEG ratio of 2.39. 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. BLK currently has a PEG ratio of 3.85.Another notable valuation metric for ATCO is its P/B ratio of 0.94. 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, BLK has a P/B of 2.96.Based on these metrics and many more, ATCO holds a Value grade of B, while BLK has a Value grade of D.ATCO sticks out from BLK in both our Zacks Rank and Style Scores models, so value investors will likely feel that ATCO is the better 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 Atlas Corp. (ATCO): Free Stock Analysis Report BlackRock, Inc. (BLK): Free Stock Analysis ReportTo read this article on Zacks.com click here.Zacks Investment Research