Investors interested in stocks from the Medical - Drugs sector have probably already heard of USANA Health Sciences (USNA) and Zoetis (ZTS). 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.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 proven Zacks Rank emphasizes companies with positive estimate revision trends, and our Style Scores highlight stocks with specific traits.Both USANA Health Sciences and Zoetis have a Zacks Rank of # 2 (Buy) right now. This means that both companies have witnessed positive earnings estimate revisions, so investors should feel comfortable knowing that both of these stocks have an improving earnings outlook. But this is just one piece of the puzzle 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 Style Score Value grade factors in a variety of key fundamental metrics, including the popular P/E ratio, P/S ratio, earnings yield, cash flow per share, and a number of other key stats that are commonly used by value investors.USNA currently has a forward P/E ratio of 15.74, while ZTS has a forward P/E of 35.28. We also note that USNA has a PEG ratio of 1.05. 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. ZTS currently has a PEG ratio of 3.15.Another notable valuation metric for USNA is its P/B ratio of 4.62. The P/B is a method of comparing a stock's market value to its book value, which is defined as total assets minus total liabilities. By comparison, ZTS has a P/B of 19.55.Based on these metrics and many more, USNA holds a Value grade of A, while ZTS has a Value grade of D.Both USNA and ZTS are impressive stocks with solid earnings outlooks, but based on these valuation figures, we feel that USNA is the superior value option right 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 USANA Health Sciences, Inc. (USNA): Free Stock Analysis Report Zoetis Inc. (ZTS): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research