In an economy that could spoil anyone's appetite, the fast-food arena serves up stellar performers alongside riskier picks. Investors should peruse the market's menu carefully before taking a bite of this sector.

Tasty fast-food stocks
Last week, McDonald's (NYSE: MCD) reported its quarterly results, once again proving that it's an industry leader. Mickey D's second-quarter net income increased 15%, to $1.41 billion, or $1.35 per share. Operating income surged 19%. Revenue increased 16%, to $6.91 billion, while total same-store sales increased an impressive 5.6%.

So far, McDonald's price increases haven't deterred its loyal customers, or broken its amazing track record of outperformance. McDonald's has raised its prices twice in the last year as it navigates the difficult tightrope between passing rising costs along to consumers and providing compelling reasons to continue frequenting the Golden Arches. So far, its adjustments seem to be working. It may try to institute some more price increases, but management appears to recognize the dangers of pushing strapped consumers too far.

Yum! Brands (NYSE: YUM) is another strong fast-food stock. My Foolish colleague Jim Royal covered its second-quarter results, and came away impressed by its eye-popping success in the coveted Chinese market, even if its domestic operations are dragging. Yum! Brands' whopping 18% comps increase in China certainly takes the sting out of its 4% domestic comps decline.

Chipotle (NYSE: CMG) suffered from rising commodity costs, but still delivered a 22.4% sales increase and a respectable 9% increase in second-quarter net income. Clearly, Chipotle's still attracting consumers with its high-quality, affordable burritos -- no easy task in the current environment.

McDonald's trades at 16 times forward earnings, while Yum! Brands sports a forward price-to-earnings ratio of 17. Chipotle surely chokes value investing types with its forward P/E ratio of 39. Are these too pricey? Before you answer, consider some of the industry's less stable players.

Beware fast-food poisoning
Beleaguered consumers and rising commodity costs now plague all quick-serve companies. Some investors may think that bargains await in the niche's beleaguered second tier -- but these prospective buyers should beware.

Wendy's (NYSE: WEN) recently ditched its Arby's acquisition, which has dragged on its financial well-being since the companies' ill-advised 2008 combination. Perhaps investors figure that things could get a lot better for Wendy's now that it's kicked Arby's to the curb. Shares have risen about 26% in the last 12 months. However, these hopes may be premature, if not wildly unrealistic.

Wendy's hasn't been able to turn a profit in the last 12 months, and its sales have fallen 3.6% in that time frame. Even if the company's making major strategic adjustments, it might be too late to regain its lost market share. Wendy's will report its latest earnings on Aug. 11.

Shares of fellow burger-slinger Sonic (Nasdaq: SONC) have risen 24% in the last 12 months. Again, investors' hopes for a better future don't match the company's present performance. Sonic's revenue fell 3.2% in the last year, and its earnings per share plunged 67.2% to $0.18 per share.

Apply a liberal grain of salt to Sonic's recent quarterly results, which emphasized an expectations-beating profit, once it stripped out certain one-time items. One of these one-time costs related to debt repayments and refinancing. When you factor such adjustments back in, Sonic reported a third-quarter loss of $4.7 million, or an $0.08 loss per share. The company staggers beneath a total debt-to-capital ratio of 93.5%.

Such stocks must be cheap though, right? Not exactly. Wendy's trades at 22 times forward earnings. Sonic's forward price-to-earnings ratio is 16. Something smells rotten here.

Go for the gold
Perhaps investors assume that stocks like Wendy's and Sonic are better "deals" because they're most known for their recent struggles, and therefore supposedly ripe for a turnaround. (You could call this the "hope premium.")

Realistically, though, these companies charge investors too high a price for futures full of serious, possibly insurmountable challenges. McDonald's or Yum! actually trade more cheaply than, or at least at similar multiples to, Wendy's and Sonic. In another bonus, McDonald's and Yum! actually perform well on many measures, and have far less risky futures.

Pursuing the leaders in a given sector can be an extremely defensive strategy, especially in today's difficult macroeconomic environment. I believe McDonald's is a stronger contender than Yum!, but they're both doing well. Chipotle may be a pricier stock overall, but it's still got abundant growth potential. And any one of these companies is a lot better than Wendy's or Sonic.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.