Investors interested in Retail - Supermarkets stocks are likely familiar with Kroger (KR) and WalMart de Mexico SAB de CV (WMMVY). 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.Kroger has a Zacks Rank of #1 (Strong Buy), while WalMart de Mexico SAB de CV 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 KR has an improving earnings outlook. But this is only part of the picture for value investors.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.KR currently has a forward P/E ratio of 12.10, while WMMVY has a forward P/E of 29.97. We also note that KR has a PEG ratio of 1.36. 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. WMMVY currently has a PEG ratio of 3.53.Another notable valuation metric for KR is its P/B ratio of 3.25. 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, WMMVY has a P/B of 7.94.These are just a few of the metrics contributing to KR's Value grade of A and WMMVY's Value grade of C.KR 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 KR is likely the superior value option right now. Infrastructure Stock Boom to Sweep America A massive push to rebuild the crumbling U.S. infrastructure will soon be underway. It’s bipartisan, urgent, and inevitable. Trillions will be spent. Fortunes will be made. The only question is “Will you get into the right stocks early when their growth potential is greatest?” Zacks has released a Special Report to help you do just that, and today it’s free. Discover 7 special companies that look to gain the most from construction and repair to roads, bridges, and buildings, plus cargo hauling and energy transformation on an almost unimaginable scale.Download FREE: How to Profit from Trillions on Spending for Infrastructure >>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 The Kroger Co. (KR): Free Stock Analysis Report WalMart de Mexico SAB de CV (WMMVY): Free Stock Analysis Report To read this article on Zacks.com click here.