Investors interested in stocks from the Banks - Foreign sector have probably already heard of Barclays (BCS) and National Australia Bank Ltd. (NABZY). But which of these two companies is the best option for those looking for undervalued stocks? Let's 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.Barclays and National Australia Bank Ltd. are sporting Zacks Ranks of #2 (Buy) and #3 (Hold), respectively, right now. This means that BCS'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 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.BCS currently has a forward P/E ratio of 5.94, while NABZY has a forward P/E of 14.93. We also note that BCS has a PEG ratio of 0.15. 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. NABZY currently has a PEG ratio of 0.62.Another notable valuation metric for BCS is its P/B ratio of 0.50. 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, NABZY has a P/B of 1.51.These are just a few of the metrics contributing to BCS's Value grade of B and NABZY's Value grade of C.BCS sticks out from NABZY in both our Zacks Rank and Style Scores models, so value investors will likely feel that BCS is the better option right now. Breakout Biotech Stocks with Triple-Digit Profit Potential The biotech sector is projected to surge beyond $2.4 trillion by 2028 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. Recommendations from previous editions of this report have produced gains of +205%, +258% and +477%. 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 Barclays PLC (BCS): Free Stock Analysis Report National Australia Bank Ltd. (NABZY): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research