I have a TA31 on my AR. The optical quality is superb (better than Leopold IMO). The TA11 has a longer eye relief that a lot of people prefer. I have my TA31 mounted with the rear eye-piece directly over the CH. There is enough room for a folding rear BUIS and the eye relief is perfect for the "nose to charging handle" form.
You can't go wrong with an ACOG. They are as solid as a rock.
Also the BAC is a pretty nifty, little mind trick, and isn't that hard to pickup on.

