i've never had either but if i had a choice it would be a ball because i personaly think there beutiful animals and have great temperments once they get over there inital shyness.
but thats just my thoughts. do some research see some pics and decide for yourself which u like best.
good luck with whatever u go with
1.2 Corns, 0.1 Ball python, 0.1.2 crested gecko's and 0.0.1 Bearded dragon