It also depends on whether you want a snake that prefers to be solitary and hide much of the time, especially if you have limited time to interact with it, or if you'd like a "display" snake that's more social and active, especially during the day. I only have one BP that will immediately pop his out of of his tub when you slide the tub out of the rack, the others are either all in their hides or diving into them because they would prefer not to be messed with.
If you're worried about a boa getting too big to handle alone, you can get a smaller variant like a dumerils, hog island, or rainbow.