A mid tower is usually enough and can fit any components. The only time a problem may arise is if you have a long video card, it can potentially conflict with the hard drive bays or with the SATA power/data cables going to the hard drives, though with a half decent mid tower, this still isn't an issue, they can fit 10"+ cards in no problem.
Full tower cases just give more room for everything. It helps to have extra room to work on your system, to fit more fans, and for fitting in water cooling, however it is more than possible to fit a decent water cooled loop in almost any mid tower case.
For instance, I upgraded from a mid ATX case to my Corsair 700D full tower. All components fit into the other case, however, the extra space is very useful when building, the internal temperatures are much lower, I can easily fit a hell of a lot more in the case, but the best thing is, I find generally it is much easier to get a plain full tower case than it is to get a mid tower. The majority of mid tower cases have some sort of design, be it colour, lights, random engravings/indentations, just something that prevents the case from having a clean, flat, professional looking finish