Individual Rack vs Whole Room Heating?

So I've been toying with the idea of enclosing a part of the basement and making it the "snake" room. I'm torn between heating the whole room versus using heated individual racks. At the present moment I heat individually and was wondering about the efficiency and cost of doing a whole room. Is it better, worse or the same? I recently visited a friend's house and he heats a small bedroom were he keeps his collection. It seems to make perfect sense to have a climate controlled area for the herps. I just don't know how cost effective it is. Any thoughts?
Terri

Well...I keep my reptile room at a steady 70 degrees and then heat my racks as anyone normally would. It provides an appropriate temperature gradation in bins, and allows me to keep multiple species that require different temperatures in the same room.

I have a "snake room" I only have corns. Temps in the room stay around 80-82. I ahven't had the "snake room" during our winter yet, but I live on the Texas coast, so it doesn't get cold here. I think if I see the temps getting too low, I'll probably place a small heater in the room.