As bomber stated, mid tower can fit most rigs. If you want water cooling or more room for HDs maybe a 2nd GPU or just more space to work with, a full tower is better but not necessary.
Its obviously bigger and therefore doesn't fit under the desk as well (in some situations) and may be a little more difficult to move around (lan parties, friends houses etc) if thats what you plan on doing with it.
Also, I think if youre planning on water cooling, its a lot easier to fit the stuff inside the case if you full tower (but i dont know much about WC).