It depends. Certainly KMart is out of the question (like seashelly said, "always a place to park").
I'd say the differences between Super Target and Super Wal-Mart are the same as the differences between regular Target and regular Wal-Mart. Target is slightly more upscale, with slightly higher prices (except they do have some really, really good clearances on clothes
). If you're just going for the basics, I'd say Wal-Mart. But Target may have some more specialized products. Honestly, though, if there were a Super Target nearby, I would probably be going there a lot more than Wal-Mart, but the closest one is 30 miles away.
But, hey. Don't tie yourself down to just one store. They both have their pros and cons, so balance it out. The only way for you to really know what's best for you is to look around at each one. And every city is different, so, it's best to just check it out for yourself.