Well typically, snakes are most vulnerable when they are eating, and for the most part, they are solitary, ambush predators who tend to hide, and many seem to prefer for smaller, more cramped quarters. Many hobbyists and breeders find the tubs seem to keep the Snakes feeling more secure, and they refuse food less. In aquariums, it is typical for a snake to feel exposed if it is visible from all sides, and it can become stressed, sick, or overly aggressive.
Tubs are safe and easy to heat with flexwatt, and also save space when utilized in Rack systems. Tubs also hold humidity much better than tanks and tend to be much much easier to clean, not having the dirt trapping corners of an aquarium/terrarium/glass tank. Tubs also tend to be shallower and so, I find it easy to approach a more aggressive snake in a shallow tub as opposed to exposing my entire arm reaching into a deep tank.
Those are the reasons I lean towards tubs. With RTB's, I would suggest an extra large rack system, as any of the common tub-and-racks systems you'll find are geared towards Balls and Colubrids, even Geckos, but there are some that do exist which are built for snakes the size of RTB's and upwards.
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