I don't know the answer to that. However it seems to me that you could set up a benchmark to find the answer to that. One piece of code would draw in a visible place, the other in a not-visible place, and you would compare the run times. (I don't think you can find elapsed CPU time, but isn't elapsed clock time what you are really interested in?)
It might turn out that the answer is "It doesn't matter" but only you can make that decision for your situation.
Joined: Jun 27, 2009
Tried myself: Rendering outside it doesn't use CPU! Yay!