I have always tried to use sights and dots. But what I have found in airsoft, is when I go for that gut reaction snap-shot I tend to pull the trigger before my line of sight fully aligns with the iron sight or optic.
And as soon as that first bb flies, my focus follows that bb and switches to the target. For some reason I ignore any part of the gun in my vision as if it were part of the background.
I take a mental note of the bb's trajectory and then compensate for it during the next trigger pull. I always have the intention of aiming properly with sights but usually end up taking red dots/acogs/magnifiers off of the gun because they tend to not be worth the extra weight.
For cqb I generally use a pistol. I seldom aim with it, I kind of extend my arm in the general direction of the target and magically my hands know what angle to hold the gun appropriately.
I guess it's kind of like being a hitter in baseball. You see the ball coming but it's mostly muscle memory that allows you to hit the ball.
The only exception where I find a red dot particularly effective is in a dark setting. Aiming at a target in the dark is much easier if your eyes don't have to adjust before firing.
Discussing this with my friends acquires the conclusion that I'm ridiculous and this is not proper for actually becoming a better player.