It doesn't have to be an "either', "or" situation, I have both. I have a large glass acquarium as my "display" tank and use if for my favorite snake who is quite tame and social. I also have a rack for my smaller/younger snakes. Both have their advantages and disadvantages but, as others have mentioned, humidity and heat CAN be maintained and regulated by covering the lid of the tank and regular mistings. Another disadvantage of tanks is that they take up a lot of space, not a big issue if you have a few but five or six mature ball pythons are going to require some large tanks and places to put them.
The rack requires less personal attention,and certainly less space, but it also completely removes any visual pleasure to be obtained from observing your snake. If you have a lot of time and just one or two animals this won't make a huge difference because it's easier to set aside time in your schedule to handle and interact with your snake. Having a rack full though, reduces the time and attention you can spend with each one.
We are fortunate that b.p. husbandry has advanced to the point where we now have housing options. The best housing options are those that result in healthy snakes.