Investors interested in stocks from the Financial - Investment Management sector have probably already heard of Principal Financial (PFG) and T. Rowe Price (TROW). But which of these two stocks is more attractive to value investors? We'll need to take a closer look to find out.There are plenty of strategies for discovering value stocks, but we have found that pairing a strong Zacks Rank with an impressive grade in the Value category of our Style Scores system produces the best returns. The Zacks Rank favors stocks with strong earnings estimate revision trends, and our Style Scores highlight companies with specific traits.Right now, Principal Financial is sporting a Zacks Rank of #2 (Buy), while T. Rowe Price has a Zacks Rank of #3 (Hold). This system places an emphasis on companies that have seen positive earnings estimate revisions, so investors should feel comfortable knowing that PFG is likely seeing its earnings outlook improve to a greater extent. But this is just one factor that value investors are interested in.Value investors also try to analyze a wide range of traditional figures and metrics to help determine whether a company is undervalued at its 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.PFG currently has a forward P/E ratio of 10.01, while TROW has a forward P/E of 16.81. We also note that PFG has a PEG ratio of 0.66. This metric is used similarly to the famous P/E ratio, but the PEG ratio also takes into account the stock's expected earnings growth rate. TROW currently has a PEG ratio of 1.87.Another notable valuation metric for PFG is its P/B ratio of 1.07. 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, TROW has a P/B of 6.24.These are just a few of the metrics contributing to PFG's Value grade of A and TROW's Value grade of C.PFG sticks out from TROW in both our Zacks Rank and Style Scores models, so value investors will likely feel that PFG is the better option right now. Breakout Biotech Stocks with Triple-Digit Profit Potential The biotech sector is projected to surge beyond $2.4 trillion by 2028 as scientists develop treatments for thousands of diseases. They’re also finding ways to edit the human genome to literally erase our vulnerability to these diseases. Zacks has just released Century of Biology: 7 Biotech Stocks to Buy Right Now to help investors profit from 7 stocks poised for outperformance. Recommendations from previous editions of this report have produced gains of +205%, +258% and +477%. The stocks in this report could perform even better.See these 7 breakthrough stocks now>>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 Principal Financial Group, Inc. (PFG): Free Stock Analysis Report T. Rowe Price Group, Inc. (TROW): Free Stock Analysis Report To read this article on Zacks.com click here.