I can't speak for the OP, but I use a similar setup. I like tubs because they are much easier to keep sterile than a terrarium. Just grab, walk it over to your outside garbage and dump, then wipe down with disinfectant. No joints with silicone to trap urates, and much lighter/easier to move. You also can also access the tubs to check on snakes or change water bowls without disturbing the snake much. Just slowly slide out the tub. No need to fumble around with locking lids. Of course, the big plus for breeders is that you can keep many snakes in a small space.
As far as the hide/perpetual darkness question, most racks are dark enough that hides are not necessary. I have a couple snakes that seemed to spend a lot of time under thier newspaper substate, so I gave them hides. They also happened to be the snakes in the top two bins, closest to the light. Wild ball pythons are in rodent burrows/termite mounds during the day and only come out at night if they are hungry or looking to breed, so perpetual darkness is not an issue. The small amount of ambient light that enters the tub during the day is enough to give them a sleep/active cycle.
Overall, I have found it easier to maintain balls in sterile conditions that also meet thier needs and make them feel comfortable in a rack system. That does not mean that BP's cannot be kept happy and clean in a terrarium, as many on this forum have success with that route as well. Hope this answers your question.