I would prefer to walk whenever possible. Reason? It's enjoyable to walk a golf course, and I feel a little more relaxed walking from shot to shot rather than hitting and jumping in a cart, speeding down the fairway.
Also easier to spit tobacco while walking.
At certain times, specifically in brutally hot weather, I'll take a cart, just so I can take extra water with me-a gallon on hot days.
In the case of Dixie Cup II, I carted it, as we played a lot of golf in a short time, with abbreviated rest-I had the feeling that I'd be pretty sapped come Sunday if I did walk.
Caddies are a nice luxury from time to time.