Investors interested in Automotive - Original Equipment stocks are likely familiar with Oshkosh (OSK) and NIU TECHADR (NIU). 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 proven Zacks Rank emphasizes companies with positive estimate revision trends, and our Style Scores highlight stocks with specific traits.Right now, Oshkosh is sporting a Zacks Rank of #2 (Buy), while NIU TECHADR has a Zacks Rank of #3 (Hold). Investors should feel comfortable knowing that OSK likely has seen a stronger improvement to its earnings outlook than NIU has recently. But this is just one factor that value investors are interested in.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.The Value category of the Style Scores system identifies undervalued companies by looking at a number of key metrics. These include the long-favored P/E ratio, P/S ratio, earnings yield, cash flow per share, and a variety of other fundamentals that help us determine a company's fair value.OSK currently has a forward P/E ratio of 18.15, while NIU has a forward P/E of 53.75. We also note that OSK has a PEG ratio of 1.04. 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. NIU currently has a PEG ratio of 1.79.Another notable valuation metric for OSK is its P/B ratio of 2.81. 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, NIU has a P/B of 16.84.Based on these metrics and many more, OSK holds a Value grade of A, while NIU has a Value grade of D.OSK has seen stronger estimate revision activity and sports more attractive valuation metrics than NIU, so it seems like value investors will conclude that OSK is the superior option right now. Breakout Biotech Stocks with Triple-Digit Profit Potential The biotech sector is projected to surge beyond $775 billion by 2024 as scientists develop treatments for thousands of diseases. They’re also finding ways to edit the human genome to literally erase our vulnerability to these diseases. Zacks has just released Century of Biology: 7 Biotech Stocks to Buy Right Now to help investors profit from 7 stocks poised for outperformance. Our recent biotech recommendations have produced gains of +50%, +83% and +164% in as little as 2 months. The stocks in this report could perform even better.See these 7 breakthrough stocks 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 Oshkosh Corporation (OSK): Free Stock Analysis Report NIU TECHADR (NIU): Free Stock Analysis Report To read this article on Zacks.com click here.