Value investing involves buying stocks that have been beaten down to well below what they're worth. However, there are times when stocks look cheap for a good reason. Family Dollar (FDO.DL) appears cheap, but is there a good reason for investors to stay away?

The worst investment in the dollar store sector
Earlier this month, Family Dollar missed earnings expectations for the second straight quarter. This time, earnings were off by 11%. All sixteen analysts following Family Dollar have lowered their expectations for the current quarter (ending in May). With the weakness that Family Dollar is seeing, it still trades relatively in-line with Dollar General (DG -0.41%) and Dollar Tree (DLTR 0.04%) from a valuation standpoint.

The potential for a buyout of Family Dollar has been buoying the stock's price. However, that talk has faded over the past couple months. Management is in flux as its COO recently left, and the company just appointed a new CMO.

All the dollar stores face certain macro pressures, including consumers' inclination to trade up to Target and Wal-Mart. One potential opportunity for the dollar stores to gain market share in is tobacco products. With CVS Caremark deciding to stop selling tobacco products, these companies should manage to capture some of that new business. Convincing shoppers to buy tobacco products at their stores versus convenience stores will likely lead to sales of other products such as consumables and personal-care products.

What about the other dollar stores?
With the potential issue of consumers trading up from dollar stores, is it wise to avoid the industry altogether? Dollar General remains the dominant leader in the space, with over 10,000 stores. That gives Dollar General an impressive advantage. However, the other aspect is that the company plans to continue expanding. It opened some 650 stores in 2013, and plans to open another 700 this year. Its large and growing store base should help it better fend off the competition.

But it's not just store expansion that's driving growth. Even its current store base is generating impressive sales. Fiscal 2013 marked the twenty-fourth consecutive year of comparable-store-sales growth for Dollar General.

Dollar Tree has the lowest store count of the three. It too missed earnings earlier this year, by just 3%, but its stock price has actually held up the best over the last month. It's also trying to catch Family Dollar when it comes to store count. Last year, it opened nearly 350 stores. The big potential disadvantage for Dollar Tree is that it has yet to offer tobacco products.

How shares stack up
As mentioned, shares of Family Dollar are holding up nicely, despite the fact that it might be the worst investment of the three. Family Dollar trades at a P/E of 17, which is the same P/E as Dollar General. Meanwhile, Dollar Tree trades at a P/E of 19.

Worth noting is that Family Dollar offers a dividend with a current yield of 2.2%. The other two don't offer a dividend. However, as we dig deeper, we find that Family Dollar has a profit margin that's 3.8%. That's well below Dollar General's 5.9% and Dollar Tree's 7.6%.

Bottom line
Dollar General remains the best bet of all the dollar stores. It has a strong, and growing, store base. With its 10,000 stores, it remains positioned the best to compete with other retailers fighting for consumers. If you're searching for the top investment in the dollar store industry, Dollar General is worth a closer look.