I have all three (well...technically I don't have my Hog yet as she's pending shipment for when it gets warmer) but like mentioned it really depends on what kind of snake you want.
Keep in mind boas will get a lot larger than balls, and will require a large enclosure. I plan on 6 feet cages for my boas: do you have the space and money for at least a 4' enclosure?
Balls are really manageable (in terms of handling and space requirements) but they can be picky eaters: so they can be unnerving if they don't eat, especially if you're used to a garbage disposal of a corn. Boas tend to not be so finicky when it comes to eating: mine have never skipped a meal.