That's a tough question. I'd like to put SD reticulated pythons at the top, but because mine are not mature yet and I know I have a good chance of some serious challenges ahead of me once adult hormones kick in, that makes me wonder if my feelings will change. Even at max size, mine are a small enough locale that it's still well within my means to deal with, but even a tiny noodle in a bad mood can be a pain when they want to be.
Of the species I've kept that I've actually gotten to experience all age ranges with, green tree pythons would be my top choice personally. Not something I would recommend to a beginner, especially in a dry climate though. It can be a heck of a chore to keep humidity right, and hatchlings are sooo fragile.