The Walmart / Sam's around here are using Fuji Frontier's, and in my opinion the Frontier is by far the best consumer lab printer out there. Results always seem consistent from different lab's running Frontier's, and there's only a subtle difference between my high end pro lab and my local Walmart because both are using the same paper and gear (Frontier).
The Walmart device likely won't be as tightly profiled for Adobe RGB, but that's rarely a problem anyways.
Take a good quality file to each shop for comparison prints, and you'll see a huge difference between the Frontier / Fuji paper and the rest.