well, i can only tell you what i have. a jungle carpet python. he is a great pet. is between 6-7 foot long. i house him in an 80 gallon size tank. he loves his big branches and hangs out on them often. is very docile with handling. i can disturb him any time and he will let me pick him up. eats great on f/t rats.
it just all depends on what you want. for me i wanted something big that i could handle by myself safely.
i considered a brazillian rainbow boa but after reading about their needs they are a bit more demanding then a JCP. i don't worry about humidity much with my JCP except when he goes into shedding mode. they i'll mist him and his tank down till he sheds.
if you can go to a reptile show/sale and you can ask all kinds of people about thier snakes. they are alot of fun. enjoy 
