I used to use large cases for all my builds (an old full tower and an Antec P180, for example), thinking that they were cooler than smaller cases. I'm sure there's some truth to this. My wife's computer, in that old full tower (Supermicro? built like a tank), has an exhausting fan on the PS, a passive HS on the graphics card (a basic one), and the Intel retail fan on the Wolfdale 8400), 3 7200 RPM hard drives, and no case fan. When I set it up I recall CPU temps being well within spec, even when I put it under a moderate load. The computer is nice and quiet, although very bulky.
On the other hand, I imagine that a properly size case, in which there is good air turnover, has its advantages and might be superior for systems that generate a lot of heat. I suppose it depends on how much of the cooling you can get through conduction (through the bulky steel case, a lot in my wife's computer's case) versus air convection.