Investors with an interest in Computers - IT Services stocks have likely encountered both CDW (CDW) and ServiceNow (NOW). But which of these two stocks is more attractive to value investors? We'll need to take a closer look to find out.The best way to find great value stocks is to pair a strong Zacks Rank with an impressive grade in the Value category of our Style Scores system. 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.Currently, CDW has a Zacks Rank of #1 (Strong Buy), while ServiceNow has a Zacks Rank of #3 (Hold). This system places an emphasis on companies that have seen positive earnings estimate revisions, so investors should feel comfortable knowing that CDW is likely seeing its earnings outlook improve to a greater extent. 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.CDW currently has a forward P/E ratio of 21.33, while NOW has a forward P/E of 110.70. We also note that CDW has a PEG ratio of 1.63. 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. NOW currently has a PEG ratio of 3.83.Another notable valuation metric for CDW is its P/B ratio of 16.64. 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, NOW has a P/B of 38.11.Based on these metrics and many more, CDW holds a Value grade of B, while NOW has a Value grade of F.CDW stands above NOW thanks to its solid earnings outlook, and based on these valuation figures, we also feel that CDW is the superior value 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 CDW Corporation (CDW): Free Stock Analysis Report ServiceNow, Inc. (NOW): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research