Chipotle Mexican Grill (NYSE:CMG) remains one of the best investments in the fast-casual dining space. During the first quarter, traffic jumped very nicely, with comparable-store sales up 13.4%. Compare this to the fact that comparable-store sales grew 1% during the first quarter of 2013.

But after trading at more than $620 a share earlier this year, shares of Chipotle are back down around $500. With the pullback, shares are trading at a P/E of 32 based on next year's earnings estimates. But this could turn out to be a great buying opportunity for investors.

Can Taco Bell take some market share?
One of Chipotle's top competitors is Yum! Brands' (NYSE:YUM)  Taco Bell. However, Yum! continues to have its own issues in China that it's working through. It gets more than half of its revenue from China. And on the domestic front, Yum! has decided to take on other fast-food chains, such McDonald's and Burger King, with its entry into the breakfast market.

David Einhorn's prediction that Taco Bell would eat into Chipotle's market share hasn't come to fruition. The reason that Taco Bell hasn't taken market share from Chipotle is that it's just too hard to compete with Chipotle's food quality, which includes genetically modified organism-free and organic, naturally raised products. And with that type of competitive advantage, Chipotle could easily expand into the breakfast market and take market share.

Not all fast-casual areas are excelling
One of Chipotle's biggest competitors on the fast-casual front is Panera Bread (NASDAQ:PNRA.DL). Panera shares are down more than 10% within the last month because Panera posted fourth-quarter results that the market wasn't terribly excited about. And since then, analysts have lowered their consensus earnings estimates for 2014 from $7.29 a share to $6.94 a share.

Panera did manage to grow revenue by 15.6% for the fourth quarter, but the worrisome issue is that comparable-store sales only grew 1.1%. That said, the company is making some changes that are worth taking note of. These include introducing new menu items (some of which are lower priced to generate more traffic) and increasing its marketing efforts.

The beauty of both Chipotle and Panera is that they cater to mid- to higher-income individuals, making the companies somewhat recession-proof. Thus, they tend to trade with higher multiples than fast-food restaurants.

Why Chipotle continues to beat out Panera
Chipotle expects to open between 180 to 195 stores in 2014. Compare that to the 115 to 125 stores that Panera plans to open. But Chipotle's current store base is expected to also help contribute to revenue growth. Chipotle's management expects comparable-store sales growth in the high-single digits for 2014.

One area that's very new for Chipotle is catering, an area that could be a key growth driver for the company. Panera is having great success with catering. Part of this comes from its introduction of online ordering for catering services.

The one potential headwind for Chipotle is rising food costs. Food costs were up 150 basis points last quarter, as prices on avocados, beef, and cheese were all higher. But Chipotle operates a 100% company-owned restaurant model, so any reduction in commodity costs will be a big positive for the business. Panera has roughly half of its restaurants franchised. 

How shares stack up
Neither Chipotle nor Panera have any meaningful debt. The returns on equity for these businesses are quite impressive, with both having a return on equity of more than 23%. Panera is now fairly cheap, trading at a forward P/E of 22 -- much cheaper than Chipotle's 32 forward P/E.

But Chipotle's expected earnings growth still beats out both Panera and Yum! Brands. Wall Street expects Chipotle to grow earnings per share at an annualized 22% over the next half decade, while expecting Panera to grow at 17.4% annually and Yum! Brands at 13.2%.

Bottom line
Chipotle is still in the early innings of its growth. It's yet to tap the catering market and ramp up the expansion of other concepts (including pizza and it Asian-inspired ShopHouse brand). For investors who are looking to get into the still fast-growing fast-casual market, they should have a closer look at Chipotle.

Marshall Hargrave has no position in any stocks mentioned. The Motley Fool recommends Chipotle Mexican Grill and Panera Bread. The Motley Fool owns shares of Chipotle Mexican Grill and Panera Bread. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.