You can got either way. Both are great snakes. Both are great display or tub snakes and both like climbing. You'll see a vast personality difference between your bp and either of these snakes. It's a great a experience.
Carpets are usually bitey if they aren't tamed down. Sometimes they are docile out of the egg. They'll typically calm down in the first year. I've dealt with a very bitey one and within a month was able to nestle itself into a bun on a girls hair. That particular snake was only 18-24 inches long.
Boas I've heard can go through a stage when maturing where if they aren't handled can develope or keep an attitude problem. NOt sure how often this happens.
Depends on preference. I prefer both. :-D