How do the Trijicon Accupoint (3x-9x), ACOG (4x only) and Aimpoint scopes compare? I'm not sure if I want the Aimpoint (no magnification? What's so good about it?) on the forward mount, or a variable or fixed ACOG on the back. Why's the ACOG so much more expensive than the accupoint?

Main use will be 3-gun matches. Thanks.

Also let's say I use an ARMS mount instead of the scout mount (I like the short barrel), can I still use the iron sights as backup, or are they totally obstructed? Can they be quickly released if the S really HTF?

Any other scopes worth considering?