I'm not sure he was asking about getting an adult one. I think both can be very high maintenance. Have you cleaned up ball python crap yet? Imagine that only MUCH BIGGER!
As far as biting, well, proper husbandry can determine some of that but the individual nature of each animal can not be overlooked. I would love to have one but in my situation it wouldn't be prudent.

I would not buy someone else's snake, unless maybe you knew them very well and knew the snake very well. You have no idea what sort of problems your buying. Buying a problem on the ball python scale is bad enough. Buying a problem in a giant is a lot worse.