For a 16" barrell, I'd use the Reflex II with 12 min triangle. (the tringle reticle allows BOTH CQB aiming, AND long range aim with the tip of the triangle)
In fact that is what I HAVE used.
The ONLY drawback of the Reflexx II is on shooting FROM a well lit area INTO a dark area (like when your in a field at noon, shooting into the forest) The triangle becomes hard to see as the daylight dims the reticle, and the darkness around you target hides the reticle.
I vote against the ACOG both due to cost (I don't think you get twice the scope with the ACOG for twice the price of the Reflex), and it looks its too scope-like - not suited to CQB, IMO (tho I've never handled one)
Can anyone comment on how well the AGOG is for CQB (snap shooting) where you can't really take the time to aim (you just place the reticle ctr mass and squeeze)???