Investors interested in stocks from the Medical - Biomedical and Genetics sector have probably already heard of Amgen (AMGN) and Illumina (ILMN). But which of these two stocks presents investors with the better value opportunity right now? Let's 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 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.Amgen has a Zacks Rank of #2 (Buy), while Illumina has a Zacks Rank of #3 (Hold) right now. The Zacks Rank favors stocks that have recently seen positive revisions to their earnings estimates, so investors should rest assured that AMGN has an improving earnings outlook. But this is only part of the picture 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.AMGN currently has a forward P/E ratio of 14.46, while ILMN has a forward P/E of 58.84. We also note that AMGN has a PEG ratio of 1.97. 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. ILMN currently has a PEG ratio of 2.66.Another notable valuation metric for AMGN is its P/B ratio of 8.80. 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, ILMN has a P/B of 14.10.These are just a few of the metrics contributing to AMGN's Value grade of B and ILMN's Value grade of D.AMGN 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 AMGN is likely 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 Amgen Inc. (AMGN): Free Stock Analysis Report Illumina, Inc. (ILMN): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research