When you examine recent McDonald's (NYSE:MCD) financial results and compare them against competitors Chipotle (NYSE:CMG) and Panera Bread (NASDAQ:PNRA) it's easy to say the two fast-casual brands are succeeding because they offer consumers food with higher perceived health value. That same argument cannot be used when you compare McDonald's continuing sales declines in the United States to Sonic's (NASDAQ:SONC) fairly explosive growth.

Both McDonald's and Sonic sell burgers, fried chicken, sugary drinks, and other typical fast-food items. You could even argue that Sonic, which also features an array of ice cream offerings, has less healthy fare. That did not stop the company that bills itself as "America's Drive-In" from posting same-store sales increases of 8.5% at franchised locations and 7.9% at company-owned stores for the quarter ending Nov. 30.

For its most recent reported quarter, which ended on Sept. 30, McDonald's same-store sales fell by 3.3% in the United States. The results were no better in October, when U.S. sales dropped by 1%, or November, when they fell by a staggering 4.6%.

Most Sonic locations do not offer in-restaurant dining. Source: Sonic. 

Sonic is about indulgence
McDonald's has in some ways been victimized by its own success. To grow sales the company had to become more than a quick place for burgers, fries, and fried chicken nuggets, all washed down with a soda or a shake. Now, McDonald's offers healthier options including salads, grilled chicken, and even yogurt parfaits.

Sonic has pretty much ignored the pressure to focus on healthier fare. It does have a grilled chicken sandwich on its "Sonic Smart" menu of items that contain 450 calories or less, but the majority of the lower-calorie choices are simply smaller portions or kids' meals. (A small order of Chili Cheese Tots has only 330 calories, but that's only a "smart" choice in relation to the rest of the menu, not food overall.)

While McDonald's is trying to serve everyone, Sonic knows it is offering an affordable indulgence, and it hits every niche of that market. Sonic has indulgent burger-based meals, ice cream treats for dessert, and even slushies and a wide variety of drinks for treating yourself when it's not precisely mealtime. 

"I think Sonic understands their core customer more than the big guys do," Stephens analyst Will Slabaugh told CNN Money. "You're typically going out to indulge. You're watching that waistline a little less and your wallet a little bit more."

Sonic is still new to many
Sonic has about 3,500 locations, all in the United States. McDonald's closed 2013 with 35,000 restaurants in over 100 countries, with roughly 14,000 U.S. locations (the company does not report specifically on its number of stores by country). That's one McDonald's for every 22,174 Americans, according to Eater.com

That level of penetration leaves it awfully hard for McDonald's to make a new store opening feel special. Sonic, on the other hand, has national ads but has not saturated much of the country. The brand has been concentrated in the South but has spread nationally in the last few years. In some locales, people have seen the company's commercials well in advance of actually getting a Sonic near where they live. That builds expectation and makes each new restaurant opening an event.

Without that advantage, McDonald's must rely on new product development to reignite customer interest. However, recent menu innovations including Mighty Wings chicken wings and the McCafe beverage line have struggled or failed outright.    

A perception of quality
While McDonald's has run the Our Food, Your Questions ad campaign to address consumer concerns over whether its meat is actually meat, Sonic has created a brand perception of offering decent quality at a fair price. The company has staked out a niche in which its customers view its menu items as better than fast-food quality, but feel like the lack of a sit-down environment creates pricing value.

"It's resonating with consumers trying to feed a family of four who don't want to pay for traditional sit downs, but also don't want to eat traditional fast food that's questionable in its quality," Robert Derrington, an analyst at Wunderlich Securities, told CNN Money

McDonald's is making changes
McDonald's has not grown to 35,000 restaurants by being unable to make changes when things are not going well. To alter its course and fix its U.S. sales, the company is testing a simplified menu. It detailed what that entails in a statement on its website:

  • Simplifying our current menu (i.e., one Quarter Pounder with Cheese burger vs. four; one Premium Chicken sandwich vs. three; one Snack Wrap vs. three.)
  • Reducing SKUs ( i.e., 16 different burgers on the menu board but we only serve two patty sizes)

"The tests are designed to determine what works and what doesn't within our restaurants by considering the operational experience, customer response, price points and other important information which may inform future decisions," according to the statement. 

That alone might not be enough to help the Golden Arches tap into some of the demand pushing Sonic, but it's bound to be better than launching another variation of a chicken wing or a slightly new take on a burger.