Investors looking for stocks in the Utility - Gas Distribution sector might want to consider either UGI (UGI) or Sempra (SRE). But which of these two stocks offers value investors a better bang for their buck right now? We'll need to take a closer look.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 proven Zacks Rank puts an emphasis on earnings estimates and estimate revisions, while our Style Scores work to identify stocks with specific traits.Right now, UGI is sporting a Zacks Rank of #2 (Buy), while Sempra has a Zacks Rank of #3 (Hold). This means that UGI's earnings estimate revision activity has been more impressive, so investors should feel comfortable with its improving analyst outlook. But this is just one piece of the puzzle for value investors.Value investors also try to analyze a wide range of traditional figures and metrics to help determine whether a company is undervalued at its 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.UGI currently has a forward P/E ratio of 22.14, while SRE has a forward P/E of 22.93. We also note that UGI has a PEG ratio of 2.77. This figure is similar to the commonly-used P/E ratio, with the PEG ratio also factoring in a company's expected earnings growth rate. SRE currently has a PEG ratio of 2.96.Another notable valuation metric for UGI is its P/B ratio of 2.14. 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, SRE has a P/B of 2.21.Based on these metrics and many more, UGI holds a Value grade of A, while SRE has a Value grade of D.UGI sticks out from SRE in both our Zacks Rank and Style Scores models, so value investors will likely feel that UGI is the better 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 UGI Corporation (UGI): Free Stock Analysis Report Sempra Energy (SRE): Free Stock Analysis Report To read this article on Zacks.com click here.