Investors with an interest in Financial - Investment Management stocks have likely encountered both Affiliated Managers Group (AMG) and BlackRock (BLK). But which of these two stocks offers value investors a better bang for their buck right now? We'll need to take a closer look.We have found that the best way to discover great value opportunities is to pair a strong Zacks Rank with a great grade in the Value category of our Style Scores system. The Zacks Rank favors stocks with strong earnings estimate revision trends, and our Style Scores highlight companies with specific traits.Currently, Affiliated Managers Group has a Zacks Rank of #2 (Buy), while BlackRock has a Zacks Rank of #3 (Hold). The Zacks Rank favors stocks that have recently seen positive revisions to their earnings estimates, so investors should rest assured that AMG has an improving earnings outlook. But this is only part of the picture for value investors.Value investors also tend to look at a number of traditional, tried-and-true figures to help them find stocks that they believe are undervalued at their current share price levels.The Value category of the Style Scores system identifies undervalued companies by looking at a number of key metrics. These include the long-favored P/E ratio, P/S ratio, earnings yield, cash flow per share, and a variety of other fundamentals that help us determine a company's fair value.AMG currently has a forward P/E ratio of 9.66, while BLK has a forward P/E of 23.62. We also note that AMG has a PEG ratio of 0.64. This popular figure is similar to the widely-used P/E ratio, but the PEG ratio also considers a company's expected EPS growth rate. BLK currently has a PEG ratio of 2.15.Another notable valuation metric for AMG is its P/B ratio of 2.24. The P/B ratio is used to compare a stock's market value with its book value, which is defined as total assets minus total liabilities. For comparison, BLK has a P/B of 3.78.These are just a few of the metrics contributing to AMG's Value grade of A and BLK's Value grade of D.AMG is currently sporting an improving earnings outlook, which makes it stick out in our Zacks Rank model. And, based on the above valuation metrics, we feel that AMG is likely the superior value option right now. Zacks' Top Picks to Cash in on Artificial Intelligence In 2021, this world-changing technology is projected to generate $327.5 billion in revenue. Now Shark Tank star and billionaire investor Mark Cuban says AI will create "the world's first trillionaires." Zacks' urgent special report reveals 3 AI picks investors need to know about today.See 3 Artificial Intelligence Stocks With Extreme Upside Potential>>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 Affiliated Managers Group, Inc. (AMG): Free Stock Analysis Report BlackRock, Inc. (BLK): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research