Image: : Starbucks coffee; McDonald’s coffee © David Goldman, AP; Dick Whipple, AP

Would you like some fries with that cinnamon dolce latte?

OK, you probably won't hear that question any time soon. But in an odd twist in the evolutionary path of quick-serve eateries, McDonald's (MCD, news) and Starbucks (SBUX, news) are looking more alike every day.

It's a trend that's going to continue, for a few simple reasons.

With a McDonald's or a Starbucks just about everywhere you look, both companies are running out of room to roam.

Starbucks was once expanding so rapidly that comedians joked it would be opening new coffee shops inside the bathrooms of existing outlets. The Seattle company plans to launch just 100 U.S. stores this year, though.

And in the cutthroat world of fast food, McDonald's needs to distance itself from powerful rivals like Burger King and Subway.

This competitive dynamic has the queen of premium coffee and the king of fast food poaching each others' customers in a low-key but persistent battle. Each is taking ideas from the other's playbook on how to please customers and boost the bottom line.

image: Michael Brush

Michael Brush

Call it the battle of the fries versus Frappuccinos. The double cheeseburger versus the double espresso. Or the Golden Arches versus the green siren. Whatever you name it, it's real, even if neither company admits it, and even if it's more a series of limited campaigns than an outright food fight.

I'll show you why, in a minute, since you might not believe it because these companies are so different.

After all, Starbucks and McDonald's have distinct customer bases -- one more affluent, the other more price sensitive. Each fan base is loyal, so there are limits to how much tinkering either of these iconic eateries can get away with. But there's plenty of middle ground -- occupied by a customer who is happy to frequent these two chains and all kinds of other fast-food joints.

So who is going to win?

It would seem that McDonald's has the most to gain. And it's easier for it to become more like Starbucks without damaging its brand than vice versa. Plus, profit margins are higher for coffee than for burgers and fries. So, the benefit to the bottom line in any victory in the coffee wars favors McDonald's, points out Pat Dorsey, the director of research and strategy at Sanibel Captiva Trust.

Make no mistake, though; Starbucks has a lot to gain as it imitates what works at McDonald's.

The other big winner just might be the consumer -- who gets higher-quality food and drinks and new amenities at McDonald's, and a bigger variety of quality food to nosh on while surfing the Internet at Starbucks.

Here's a closer look at the battle between these quick-serve giants.

The coffee wars

Early on, burgers and fries, and later breakfast meals were strengths for McDonad's. Drinks were an afterthought. It took a while, but the chain noticed the big profits Starbucks was raking in from coffee sales. McDonald's knew it could never get away with $5 coffee drinks. Well aware of its customer base, McDonald's is "always keeping an ever-vigilant eye on everyday affordability, which is the most important thing for our consumers," CEO Jim Skinner said during the company's most recent conference call with shareholders. "They get pinched everywhere," Skinner added. "They should not suffer the same fate at McDonald's."

But, taking a page from the Starbucks playbook, McDonald's has rolled out premium coffee. It's been a big hit, and it is growing by leaps and bounds. During the first quarter, sales of "specialty coffees" increased 17% from a year earlier. "We believe McDonald's could evolve into Starbucks' fiercest rival in the specialty coffee segment," says analyst R.J. Hottovy, who covers both companies for Morningstar.

This puts Starbucks in a quandary. It's got to be careful not to cheapen its brand, yet it needs to respond to this challenge from McDonald's. So far, Starbucks has finessed the matter well. It went after McDonald's coffee customers with a rollout of its premium coffee brand Seattle's Best Coffee at more than 30,000 quick-service competitors of McDonald's, such as Subway. This gives the company exposure to this space without putting the Starbucks name into the fray.

By stealthily moving into this part of the market, Starbucks looks more like McDonald's, at least behind the scenes, without diluting the premium aspects of its name in the eyes of the public. Job well done.