Well, it really just boils down to taste. They are both very calm and move slowly and deliberately. If you want a python that is just going to sit in your hands the way a lap dog sits on your lap then a ball python is good. If you want something with a bit more personality then I would get a spotted. Both generally have good dispositions and seldom bite, even as babies. I have handled tons of babies of both species and neither have ever attempted to bite. They get about the same length but a ball is much more massive and heavy bodied which justifies a larger set up. Here are some pics of my baby Cape York Spotteds and their shoebox.



-----