I don't have experience with large boas, but I love my rosys. They are quite a bit smaller than ball pythons (adults only get 2-3 feet), more friendly, and they don't require as much humidity. They're typically more active when handled. They'll slither right up to your face and sniff your nose with their tongues if you let them! But they're also very slow so there's no need to worry about them being squirmy or making a "quick" getaway.
They're also great snakes for a typical tank setup, since they like low humidity you won't have to modify a glass tank to hold it in like you would for a ball python. As far as eating goes, they're not picky. My first rosy was on live mice for four years when I got him. I offered a frozen/thawed mouse and he took it right away. They tend to have regurgitation issues if humidity is high though, so if you live in a humid area they may not be the best pet for you.
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