I prefer off, since I am usually more uninhibited this way, but on still is fine. Some of my favorite quickies have been during the day in full light, so it's not all bad.
Normally it doesn't really matter either way! Now that I haven't been able to work out regularly & I haven't lost all my stomach from Bink I find myself preferring off. Unless I just want it bad & just don't care or am drunk, LOL.