tank or tub ?

It all comes down to collection size. If you are looking at starting a collection with multiple aninals then a rack with tubs is the best option. If your just workin with one or two animals then go with a good cage system. It doesnt matter about cage size. You can get proper temps and humidity out of any size cage. Bigger cages just take more to donit thats all.

Plus ball pythons aren't the best display animal. They stay in their hides all day if they're happy. If I wanted a display animal I would go with a green tree python because they're gorgeous and will sit out on their branch all day in plain sight. And I would give it a big, beautiful vivarium. But balls tend to be much more secure and happy in tub, as well as the fact that it's easier to maintain the proper habitat for a ball in a tub.