I have never tried a Walmart cake so I can not comment. Years ago, I used to buy the Publix white cakes which used to be pretty good. I have not bought a store cake in many years but I prefer now to make my own.
I used to make the boxed cakes but once they cut down their ingredients I started to make everything from scratch. Everyone who has tasted my cakes say they love the scratch cakes much better than the grocery store cakes. I guess to each his own.