You can't judge a snake's true "size" on its length.

A 5-6 foot BRB may weigh exactly the same as a 3 foot RTB or a 9 foot blue beauty ratsnake. BRBs stay MUCH smaller in both weight and length (particularly in length) than RTBs and dumerils.

We have a pair of brazilian rainbow boas, and they were a great first snake species for my girlfriend. They're a little more demanding so not quite as boring as your typical corn snake or ball python, and SUPER beautiful!

The experience you get from BRBs is completely different than heavy bodied red tailed boas or dumerils. If you want a big, heavy snake, go with the RTB or dumerils. If you don't, a BRB is a good choice.