There is a noticble difference, not all pythons are rocks like BP's are. Carpet pythons are more active than ball Pythons but less active than most boas. And not all Boas are super active. My Dumeril's will just sit in my hand.
Here is some info on carpets
http://www.acreptiles.com/main/index...=81&Itemid=140
Ball Pythons, Boas, and Carpet Pythons are all great. Individuals from all 3 can be aggressive or extremely docile. You can't go wrong with any of them you just have to find what you want (size, how active, looks, and care requirements) that fit you