I recently got an adult, albino rosy boa. So far she has been great. I've heard from many that they tend to be very docile, and have heard mixed things about Kenyans, some say very good things, others say they are very aggressive, I have no personal experience with them, but that's what I've heard. The reason I got a rosy over a Kenyan is that you will tend to see rosy's more in their vivarium. Kenyans burrow a lot more, whereas my rosy likes to be above-ground a lot of the time, but also burrows a bit as well. They are also a great size, reasonably long, but also somewhat thick, which makes them slower and easier to handle. But, I've never handled a Kenyan, so I don't know how they compare, all I know is that she is very fun to handle, and is also very curious.

From research I can tell you that male Kenyans can be kept in a 10 gallon, as they are a bit smaller. You also have to remember to take floor space into account more than the tank size, a tank with a larger base and less vertical space will be best, as they are limited by their substrate. Rosy's should definitely be kept in 20 gallons or larger. I personally keep mine in a 20 gallon, with a few inches of shredded aspen so she can burrow. I would have gone with a 30 gallon breeder to allow for more floor space, but Rosy's are somewhat pricey, so I decided to go with a 20 for now, and may upgrade to a 30 gallon later. My rosy is very curious, so I also put a few plastic plants and some fake vines for her to climb around on. They are desert snakes, but she seems to enjoy slithering up the side of her tank, and does wander around the plants from time to time.

Good luck and best wishes for whichever one you decide to get!