Investors interested in stocks from the Oil and Gas - Production and Pipelines sector have probably already heard of Ultrapar Participacoes S.A. (UGP) and Enbridge (ENB). But which of these two companies is the best option for those looking for undervalued stocks? Let's take a closer look.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 proven Zacks Rank puts an emphasis on earnings estimates and estimate revisions, while our Style Scores work to identify stocks with specific traits.Currently, Ultrapar Participacoes S.A. has a Zacks Rank of #2 (Buy), while Enbridge has a Zacks Rank of #3 (Hold). Investors should feel comfortable knowing that UGP likely has seen a stronger improvement to its earnings outlook than ENB 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.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.UGP currently has a forward P/E ratio of 14.10, while ENB has a forward P/E of 18.58. We also note that UGP has a PEG ratio of 0.62. 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. ENB currently has a PEG ratio of 3.10.Another notable valuation metric for UGP is its P/B ratio of 1.57. 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, ENB has a P/B of 1.93.These metrics, and several others, help UGP earn a Value grade of A, while ENB has been given a Value grade of C.UGP stands above ENB thanks to its solid earnings outlook, and based on these valuation figures, we also feel that UGP is the superior value option right now. Want to Know the #1 Semiconductor Stock for 2022? Few people know how promising the semiconductor market is. Over the last couple of years, disruptions to the supply chain have caused shortages in several industries. The absence of one single semiconductor can stop all operations in certain industries. This year, companies that create and produce this essential material will have incredible pricing power. For a limited time, Zacks is revealing the top semiconductor stock for 2022. You'll find it in our new Special Report, One Semiconductor Stock Stands to Gain the Most. Today, it's yours free with no obligation.>>Give me access to my free special report.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 Ultrapar Participacoes S.A. (UGP): Free Stock Analysis Report Enbridge Inc (ENB): Free Stock Analysis Report To read this article on Zacks.com click here.