I two have used both, but prefer a red dot for shots up to 100yrds.
I have a leopold gilmore and I think the dot is only 2 MIA, which does not impede site picture, most red dots have way too big a dot.
My father, who has vision problems, shot at 6 clay pigeons I had layed out at 100yrds his first time shooting my .44 super redhawk and hit 5 of the 6 targets.
He would not have been able to do that with open sites or a scope, because he can't focus in close with one eye shut. The red dot allows you to keep both eyes open and just place the dot on the target.
For longer shots, or smaller targets I far prefer a scope of 1.5-4 power on a handgun, but for deer up to 100, in all light conditions, the red dot is hard to beat. Most TC situations require a scope for me, since I am in CA and many shots will be out to 200yrds. My redhawk is my close in bear, dear and pig gun when shots may be very close and require super quick follow ups. I just am not fast enough at loading the TCs yet at 10yrds with a mad pig or bear looking at me.
On the other hand, some states do not allow any site device that is battery powered, plus there is always the possibility of the batteries going dead. I carry an extra battery, but it would be very inconvienant to have to change it right when a shot presents itself.
Brian