Bodies can be altered far more easily. If you don't have a hot body, you can get one. Granted you can't change some things (height, proportions etc) but it's much more workable. If you have an ugly face then surgery is the only option.
Face. It's very had to change your face, although with plastic surgery, which is expensive, it may not work out the way you want it to.
The body. You can EASILY change that quickly. So if you're a slob, you can get a beach bod in 2 months by working out regularly. Cheaper than plastic surgery.
Both.
I wouldn't date nor fool around with someone gorgeous that is fat or too skinny nor I would do it with someone with the hottest body ever but with an ugly face.