Investors looking for stocks in the Containers - Paper and Packaging sector might want to consider either Berry Global (BERY) or AptarGroup (ATR). But which of these two stocks presents investors with the better value opportunity right now? 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 favors stocks with strong earnings estimate revision trends, and our Style Scores highlight companies with specific traits.Currently, Berry Global has a Zacks Rank of #2 (Buy), while AptarGroup has a Zacks Rank of #3 (Hold). This system places an emphasis on companies that have seen positive earnings estimate revisions, so investors should feel comfortable knowing that BERY is likely seeing its earnings outlook improve to a greater extent. But this is only part of the picture for value investors.Value investors are also interested in a number of tried-and-true valuation metrics that help show when 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.BERY currently has a forward P/E ratio of 11.42, while ATR has a forward P/E of 33.84. We also note that BERY has a PEG ratio of 1.14. 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. ATR currently has a PEG ratio of 4.83.Another notable valuation metric for BERY is its P/B ratio of 3.35. The P/B ratio pits a stock's market value against its book value, which is defined as total assets minus total liabilities. For comparison, ATR has a P/B of 4.88.These metrics, and several others, help BERY earn a Value grade of A, while ATR has been given a Value grade of C.BERY stands above ATR thanks to its solid earnings outlook, and based on these valuation figures, we also feel that BERY is the superior value 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 Berry Global Group, Inc. (BERY): Free Stock Analysis Report AptarGroup, Inc. (ATR): Free Stock Analysis Report To read this article on Zacks.com click here.