Investors looking for stocks in the Staffing Firms sector might want to consider either GEE Group Inc. (JOB) or Insperity, Inc. (NSP). But which of these two companies is the best option for those looking for undervalued stocks? 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 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, GEE Group Inc. is sporting a Zacks Rank of #2 (Buy), while Insperity, Inc. has a Zacks Rank of #5 (Strong Sell). Investors should feel comfortable knowing that JOB likely has seen a stronger improvement to its earnings outlook than NSP has recently. But this is only part of the picture 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 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.JOB currently has a forward P/E ratio of 9.33, while NSP has a forward P/E of 22.59. We also note that JOB 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. NSP currently has a PEG ratio of 1.51.Another notable valuation metric for JOB is its P/B ratio of 0.65. 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, NSP has a P/B of 120.03.These metrics, and several others, help JOB earn a Value grade of A, while NSP has been given a Value grade of C.JOB is currently sporting an improving earnings outlook, which makes it stick out in our Zacks Rank model. And, based on the above valuation metrics, we feel that JOB is likely the superior value option right now. Zacks Names "Single Best Pick to Double" From thousands of stocks, 5 Zacks experts each have chosen their favorite to skyrocket +100% or more in months to come. From those 5, Director of Research Sheraz Mian hand-picks one to have the most explosive upside of all. It’s a little-known chemical company that’s up 65% over last year, yet still dirt cheap. With unrelenting demand, soaring 2022 earnings estimates, and $1.5 billion for repurchasing shares, retail investors could jump in at any time. This company could rival or surpass other recent Zacks’ Stocks Set to Double like Boston Beer Company which shot up +143.0% in little more than 9 months and NVIDIA which boomed +175.9% in one year.Free: See Our Top Stock and 4 Runners Up >>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 GEE Group Inc. (JOB): Free Stock Analysis Report Insperity, Inc. (NSP): Free Stock Analysis Report To read this article on Zacks.com click here.