I also have to vote BRB... no bias at all of course!!They do require higher humidity than a RTB, but really if you get a tub the humidity is so easy to keep up. My little guy is only about 5 months old now and since the initial misting of the bedding, I only have to mist once a week and he's been doing wonderfully. Total sweetheart too, very curious and active.
ATBs are beautiful, but the attitude does turn me off a bit. I suppose if you don't mind that kind of snake, then they're great. I would like to get a green tree python at some point though... I've heard more stories about them being a little more friendly than ATBs and they're just as gorgeous. All of these snakes (BRBs, ATBs and GTPs) require high humidity and specific temps though, so basically it's all about the temperament you're looking for.