There have been a few controlled-condition tests made with a variety of shooters, comparing the speed of an accurate shot at close range. In every one I've seen, the scopes won.
This may be due to most shooters not being all that practiced with irons these days, but is also due to the fact that a low-powered scope provides a single aiming point, while irons have two points that must be aligned. The rare exception is when a rifle is specifically fitted to an indivudal shooter so the front sight can be used for reasonably accurate aiming. I set up my .416 Rigby this way, but it's still no faster than a low-power scope-.
