How good those Walmart kits are depends on what you're keeping and what your preferences are.
I don't like them because:
*the openings in the back of the hood are too big, so evaporation is quick and fish have lots of room to jump out and die.
*the heaters are All-Glass heaters which are no good in my experience. Mine wouldn't let my water get below 82F no matter what I set the dial on, the heater was very hot to the touch, and fish that get stuck behind it get burned if not killed.
*I'd rather buy a bare tank and pick out better quality equipment to put in it, because if you're much of an enthusiast, you will replace it all in the long run anyway.