According to a report Monday in The Arizona Republic, Whole Foods Market (NASDAQ:WFMI) is planning to open two 60,000-square-foot stores outside of Phoenix. That's more than double the size of many of its existing stores.

The new, larger stores will dedicate most of the additional space to prepared food offerings -- including tapas and freshly cooked meats -- that customers select themselves. It appears the expanded offerings will also include a wine bar, beer, and additional seating.

What I find interesting is that while Whole Foods is an up-market grocery store, it is still a grocery store. Now it is adding square feet and essentially adding a number of restaurant-like offerings. So you have a grocery store with a restaurant-like twist. Color me unimpressed.

Whole Foods has developed its brand very well, but at the end of the day there's very little Whole Foods does which cannot be copied by other grocers or restaurants. Some grocers such as Trader Joe's successfully compete with better prices and Delhaize (NYSE:DEG), which is best known as Food Lion, is rolling out Bloom grocery shops as a competitive offering. Whole Foods' ability to offer more prepared organic and fresh foods does separate it from most restaurants, which don't focus on organics. But like the grocery stores, anybody can do it.

Now, Starbucks (NASDAQ:SBUX) was labeled just a coffee shop in its early days, and it has managed to thrive ... so the logical argument is that Whole Foods could be the same story. But one thing separates Starbucks and Whole Foods, and that is return on invested capital.

Leaving leases out of the equation, I estimate Whole Foods earns somewhere between 12% and 14% on its invested capital. That's respectable, but hardly a sign of a world-beating competitive advantage. Add in leases, and the returns drop into the high single digits. Starbucks' return on invested capital is 20% without leases, and around 13% with leases included.

It's important to note that these large stores with expanded offerings are early in the development phase for Whole Foods, and the company can pull the plug at any time. But I'd be surprised if the large format stores earn returns above what the company gets from its current store base, and it has some improvement to do there as well.

Whole Foods and Starbucks are both Motley Fool Stock Advisor recommendations.

Nathan Parmelee owns shares in Starbucks. The Motley Fool has an ironclad disclosure policy.