Re: I need help with a decision...
I haven't personally kept arboreals or BRB's, but here is two cents anyways...
Arboreals are by far the best display snakes, but are not great for taking out of the cage and handling (of course there are exceptions, but in general GTP's are not friendly snakes). BRB's can be nippy, but most grow to be pretty docile and are great for handling. Yes, humidity/mold/bacteria are issues for both, but with a little extra maintenance and supervision, it's perfectly doable.
They're both gorgeous snakes, and I think it really comes down to whether you're looking for visibility but not much handling or handling but not great visibility.