Investors interested in Transportation - Services stocks are likely familiar with Schneider National (SNDR) and Grupo Aeroportuario del Sureste (ASR). But which of these two stocks is more attractive to value investors? We'll need to take a closer look to find out.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 favors stocks with strong earnings estimate revision trends, and our Style Scores highlight companies with specific traits.Currently, Schneider National has a Zacks Rank of #2 (Buy), while Grupo Aeroportuario del Sureste has a Zacks Rank of #3 (Hold). Investors should feel comfortable knowing that SNDR likely has seen a stronger improvement to its earnings outlook than ASR has recently. 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.The Style Score Value grade factors in a variety of key fundamental metrics, including the popular P/E ratio, P/S ratio, earnings yield, cash flow per share, and a number of other key stats that are commonly used by value investors.SNDR currently has a forward P/E ratio of 12.66, while ASR has a forward P/E of 27.46. We also note that SNDR has a PEG ratio of 0.91. This popular figure is similar to the widely-used P/E ratio, but the PEG ratio also considers a company's expected EPS growth rate. ASR currently has a PEG ratio of 6.24.Another notable valuation metric for SNDR is its P/B ratio of 1.80. The P/B ratio pits a stock's market value against its book value, which is defined as total assets minus total liabilities. For comparison, ASR has a P/B of 2.59.Based on these metrics and many more, SNDR holds a Value grade of A, while ASR has a Value grade of D.SNDR has seen stronger estimate revision activity and sports more attractive valuation metrics than ASR, so it seems like value investors will conclude that SNDR is the superior option right now. 5 Stocks Set to Double Each was hand-picked by a Zacks expert as the #1 favorite stock to gain +100% or more in 2021. Each comes from a different sector and has unique qualities and catalysts that could fuel exceptional growth. Most of the stocks in this report are flying under Wall Street radar, which provides a great opportunity to get in on the ground floor. Today, See These 5 Potential Home Runs >>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 Schneider National, Inc. (SNDR): Free Stock Analysis Report Grupo Aeroportuario del Sureste, S.A. de C.V. (ASR): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research