Investors interested in Utility - Gas Distribution stocks are likely familiar with MDU Resources (MDU) and New Jersey Resources (NJR). But which of these two stocks presents investors with the better value opportunity right now? 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 favors stocks with strong earnings estimate revision trends, and our Style Scores highlight companies with specific traits.Right now, both MDU Resources and New Jersey Resources are sporting a Zacks Rank of # 2 (Buy). This means that both companies have witnessed positive earnings estimate revisions, so investors should feel comfortable knowing that both of these stocks have an improving earnings outlook. 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.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.MDU currently has a forward P/E ratio of 15.30, while NJR has a forward P/E of 23.06. We also note that MDU has a PEG ratio of 2.72. 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. NJR currently has a PEG ratio of 3.84.Another notable valuation metric for MDU is its P/B ratio of 2.04. 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, NJR has a P/B of 2.25.Based on these metrics and many more, MDU holds a Value grade of B, while NJR has a Value grade of D.Both MDU and NJR are impressive stocks with solid earnings outlooks, but based on these valuation figures, we feel that MDU 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 MDU Resources Group, Inc. (MDU): Free Stock Analysis Report NewJersey Resources Corporation (NJR): Free Stock Analysis Report To read this article on Zacks.com click here.