Investors with an interest in Retail - Discount Stores stocks have likely encountered both Big Lots (BIG) and Ross Stores (ROST). But which of these two stocks presents investors with the better value opportunity right now? Let's 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 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.Right now, Big Lots is sporting a Zacks Rank of #2 (Buy), while Ross Stores 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 BIG has an improving earnings outlook. However, value investors will care about much more than just this.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 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.BIG currently has a forward P/E ratio of 12.63, while ROST has a forward P/E of 32.09. We also note that BIG has a PEG ratio of 1.13. 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. ROST currently has a PEG ratio of 3.21.Another notable valuation metric for BIG is its P/B ratio of 2.05. 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, ROST has a P/B of 14.31.These metrics, and several others, help BIG earn a Value grade of A, while ROST has been given a Value grade of C.BIG sticks out from ROST in both our Zacks Rank and Style Scores models, so value investors will likely feel that BIG is the better 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 Big Lots, Inc. (BIG): Free Stock Analysis Report Ross Stores, Inc. (ROST): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research