Investors with an interest in Manufacturing - General Industrial stocks have likely encountered both Altra Industrial Motion (AIMC) and Parker-Hannifin (PH). 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.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 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.Right now, both Altra Industrial Motion and Parker-Hannifin are sporting a Zacks Rank of # 2 (Buy). This system places an emphasis on companies that have seen positive earnings estimate revisions, so investors should feel comfortable knowing that these stocks have improving earnings outlooks. But this is just one factor that value investors are interested in.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.Our Value category grades stocks based on a number of key metrics, including the tried-and-true P/E ratio, the P/S ratio, earnings yield, and cash flow per share, as well as a variety of other fundamentals that value investors frequently use.AIMC currently has a forward P/E ratio of 16.71, while PH has a forward P/E of 21.48. We also note that AIMC has a PEG ratio of 1.11. 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. PH currently has a PEG ratio of 1.82.Another notable valuation metric for AIMC is its P/B ratio of 1.88. 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, PH has a P/B of 5.26.Based on these metrics and many more, AIMC holds a Value grade of B, while PH has a Value grade of C.Both AIMC and PH are impressive stocks with solid earnings outlooks, but based on these valuation figures, we feel that AIMC 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 Altra Industrial Motion Corp. (AIMC): Free Stock Analysis Report ParkerHannifin Corporation (PH): Free Stock Analysis Report To read this article on Zacks.com click here.