I would go with the amazon tree boa. I would tell you the same thing if I responded in the other forum you posted in. I would never pay for a RTB since there are so many in need of adoption and the aquatic behavior of the anacondas is not all its wrapped up to be. It is a pain to clean big water tubs and they dont use it as much as you would think. Its just a mess. You have to go with what you love. And everyone loves amazon tree boas except my girlfriend. She thinks they are too skinny. She likes anacondas. (and she weighs 90 lbs...who is she to talk about too skinny)
This post if of course light hearted and nobody can tell you what kind of snake you want. There are great things about them all and you really need to go with what your passion is. But if it is a RTB you should look for one in need of a hone.