If you raise your boa from a hatchling you shouldn’t have any issues handling it as an adult. Boas grow fairly slowly, if they’re not overfed, so you’ll have a few years experience with the animal before it hits the 6’ mark. My boas are both in the 4’ range right now, I also have a few 7-8’ pythons. The pythons aren’t quite as heavy bodied as the boas but I think they’re more challenging to handle. Their tails have a mind of their own. Most boas move pretty slowly and will sometimes even stay still during handling while pythons are much more active. IMO boas are easier and slightly more fun to handle.