I have a Nelson's and a Pueblan, and really.. the type of snake won't determine temperament. It's really the individual critter that says it all.

If you hold them, whichever one is the least flighty and crazy trying to get out of your hands is the best. My pueblan is nutso and hasn't calmed down yet, and my nelson's is a doll and goes grocery shopping with me. :]

Big warning: make sure your cage has so many locks a polar bear couldn't escape it. And always always always shut it, these guys are real houdinis.