I'm going to go against the grain and advocate the red dot here for general purpose use. I have one on both my shotty and the .308 battle rifle.
A scope is fine for precision work at any range, but I don't like two things about it for fast shots: limited field of vision, and the necessity for pproper eye relief. If you only punch paper, or you need to zap a critter of any kind at 300+ yards *and* have time to line 'em up perfectly, then the scope is superior to the red dot sight.
For social work and hunting, however, I think that the red dot has it all over the scope. You can keep both eyes open, you don't need proper eye relief, and target acquisition for quick "snap shots" is much faster with a red dot sight. In addition, the red dot will work well in low light or complete darkness, and even a 4 or 5MOA dot will be just as precise as a front sight post. For distances from 0-200 yards, which is where most of the social and hunting work happens, the red dot/holosight etc. is superior to scope and iron sights.
If you ran a military course of fire with iron sights, then a scope, and then a red dot, there's no doubt in my mind that you'd be nailing the most targets in the fastest time with a red dot-equipped rifle.