this.
My actual preference is for an aimpoint at distances 200.yards and in. anything further or for precision I like magnification like the acogs. It all depends on the intended use.
Well I guess all I have to offer is I have an EO Tech 512 and I love it. It sits on top of a RRA flat top and I have had absoloutely no trouble with it. It is easy to setup, zero and will take a lot of abuse. I like it. I dont know about ACOGs but thats cause I have no experience. I will say this....the one I have is a no magnification. And with my old eyes getting a good sight picture with out magnification can be tricky. If I di it again I will probably look at a 3X or 4X.
I think from a pure versatility standpoint you can't go wrong with one of the various 1-4x variable scopes out. You get red dot speed at lose range and still have a degree of precision for longer shots. They can be had from $300-3000 depending on budget. 3 gunners are arguably harder on thier weapons than even the military. If they hold up for them, you can't go wrong.
Have you taken a look at the trijicon accupooint scopes? They have different magnifications out. There is a real nice 1x4 that you might enjoy. I asked about these scopes and seems like some members use the 1x4 for 3gun and really like them. I went with the 3x9 and love it. They are a lot more affordable then some of than the acogs.
Look at all the 1-4x options. Burris XTR, Vortex Viper PST, Nightforce, trijicon accupoint, etc.. Most of these are good options. I have first hand experience with the XTR and PST, and they are both great optics.