Investors with an interest in Retail - Apparel and Shoes stocks have likely encountered both Tilly's (TLYS) and Gap (GPS). 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 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.Tilly's and Gap are sporting Zacks Ranks of #2 (Buy) and #3 (Hold), respectively, right now. Investors should feel comfortable knowing that TLYS likely has seen a stronger improvement to its earnings outlook than GPS has recently. But this is just one piece of the puzzle 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 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.TLYS currently has a forward P/E ratio of 12.20, while GPS has a forward P/E of 18.38. We also note that TLYS has a PEG ratio of 1.22. 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. GPS currently has a PEG ratio of 1.53.Another notable valuation metric for TLYS is its P/B ratio of 2.76. 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, GPS has a P/B of 4.35.These metrics, and several others, help TLYS earn a Value grade of B, while GPS has been given a Value grade of C.TLYS 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 TLYS is likely the superior value option right now. Bitcoin, Like the Internet Itself, Could Change Everything Blockchain and cryptocurrency has sparked one of the most exciting discussion topics of a generation. Some call it the “Internet of Money” and predict it could change the way money works forever. If true, it could do to banks what Netflix did to Blockbuster and Amazon did to Sears. Experts agree we’re still in the early stages of this technology, and as it grows, it will create several investing opportunities. Zacks’ has just revealed 3 companies that can help investors capitalize on the explosive profit potential of Bitcoin and the other cryptocurrencies with significantly less volatility than buying them directly. See 3 crypto-related stocks 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 Tillys, Inc. (TLYS): Free Stock Analysis Report The Gap, Inc. (GPS): Free Stock Analysis Report To read this article on Zacks.com click here.