I got a BCI boa after I got my ball python. I had the BP for about 1.5 years before doing that. I'm very glad I did. The attitude and personality is a LOT different, and occasionally, rarely, aggressive.
Don't let that worry you though, I have so much fun with my boa, he's great. The different personality and a bit of "take no crap" attitude is great.
I also have a Northern Pine Snake, which generally (not always) have even more attitude and personality. Some of them are fairly nasty, you gotta watch out. But mine is very calm and rarely gets mad at me, but it's so cute when he does: he rattles his tail against something trying to be a rattlesnake! Daaw.
http://www.youtube.com/watch?v=WBjHE78fyrQ&fmt=22
He's also VERY curious and wants to see, explore, and crawl on everything. He gets a little annoyed when I don't let him and gently puffs some air out his nostrils. It sounds like a little kid getting annoyed.
So, all I can speak for is BCI boas and northern pines, but I recommend both. Just do your research, you'll be fine no matter what you get.