Investors interested in Medical - Drugs stocks are likely familiar with Jazz Pharmaceuticals (JAZZ) and Zoetis (ZTS). But which of these two companies is the best option for those looking for undervalued stocks? Let's take a closer look.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.Currently, Jazz Pharmaceuticals has a Zacks Rank of #2 (Buy), while Zoetis 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 JAZZ has an improving earnings outlook. But this is just one factor that value investors are interested in.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.Our Value category highlights undervalued companies by looking at a variety of key metrics, including the popular P/E ratio, as well as the P/S ratio, earnings yield, cash flow per share, and a variety of other fundamentals that have been used by value investors for years.JAZZ currently has a forward P/E ratio of 9.45, while ZTS has a forward P/E of 34.53. We also note that JAZZ has a PEG ratio of 0.84. 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 2.84.Another notable valuation metric for JAZZ is its P/B ratio of 2.78. 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, ZTS has a P/B of 22.17.These metrics, and several others, help JAZZ earn a Value grade of A, while ZTS has been given a Value grade of C.JAZZ stands above ZTS thanks to its solid earnings outlook, and based on these valuation figures, we also feel that JAZZ 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 Jazz Pharmaceuticals PLC (JAZZ): Free Stock Analysis Report Zoetis Inc. (ZTS): Free Stock Analysis Report To read this article on Zacks.com click here.