Investors looking for stocks in the Transportation - Services sector might want to consider either TFI International Inc. (TFII) or Grupo Aeroportuario del Pacifico (PAC). But which of these two stocks is more attractive to value investors? We'll need to take a closer look to find out.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 proven Zacks Rank emphasizes companies with positive estimate revision trends, and our Style Scores highlight stocks with specific traits.TFI International Inc. and Grupo Aeroportuario del Pacifico are sporting Zacks Ranks of #1 (Strong Buy) and #2 (Buy), respectively, right now. This system places an emphasis on companies that have seen positive earnings estimate revisions, so investors should feel comfortable knowing that TFII is likely seeing its earnings outlook improve to a greater extent. However, value investors will care about much more than just this.Value investors also tend to look at a number of traditional, tried-and-true figures to help them find stocks 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.TFII currently has a forward P/E ratio of 12.15, while PAC has a forward P/E of 19.31. We also note that TFII has a PEG ratio of 0.60. 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. PAC currently has a PEG ratio of 1.76.Another notable valuation metric for TFII is its P/B ratio of 3.70. 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, PAC has a P/B of 9.07.These are just a few of the metrics contributing to TFII's Value grade of B and PAC's Value grade of D.TFII has seen stronger estimate revision activity and sports more attractive valuation metrics than PAC, so it seems like value investors will conclude that TFII is the superior option right now. Special Report: The Top 5 IPOs for Your Portfolio Today, you have a chance to get in on the ground floor of one of the best investment opportunities of the year. As the world continues to benefit from an ever-evolving internet, a handful of innovative tech companies are on the brink of reaping immense rewards - and you can put yourself in a position to cash in. One is set to disrupt the online communication industry. Brilliantly designed for creating online communities, this stock is poised to explode when made public. With the strength of our economy and record amounts of cash flooding into IPOs, you don’t want to miss this opportunity.>>See Zacks’ Hottest IPOs NowWant 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 TFI International Inc. (TFII): Free Stock Analysis Report Grupo Aeroportuario Del Pacifico, S.A. de C.V. (PAC): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research