My one and only coastal carpet python is named Kitty, and she is every bit as sweet as her name implies. The first week I had her she would hiss and puff if I disturbed her, but once she got over the post-shipping jitters, she quickly became the sweetest and best-handling snake I've ever experienced. The general saying with carpet pythons is that 'babies are generally nippy but will settle down very nicely as they age'.
Carpet pythons are NOT BPs though. They won't just sit in your lap and do nothing while you watch TV for an hour. They're fairly active and aware, and while they don't move fast, they do constantly move.
If you've narrowed it down to dumerils, carpets, and SD 'tics, I'd say they're all great choices, and all fairly different snakes. I've met nippy ones of all 3 species and I've met easily handled ones of all species.
I agree with Al that BCIs and BCCs are great snakes too, and if you're considering Dumerils, I'd keep those on the 'possible' list too.