If I had to have an AR-15 type pistol, I would rather have one like the Olympic Arms version... I just can't stand that recoil buffer tube hanging out the back. The lines on the OA just look cleaner (to me).
I assume that's an OA brand pistol that Willem Defoe uses in "Clear and Present Danger", since I'm not aware of another brand with the recoil spring over the barrel... Of course, I've been known to be WRONG
This same version made a big appearance in one of the "Batman" sequels too. (The one with 2-face, I believe). This time, they got a "neon upgrade" and sported 90 round drum mags... Wouldn't THAT be fun
On the other hand, (and this is just my little ole' opinion again) If I were going to get a Professional Ordnance weapon, I'd probably opt for one of their lightweight rifles. Since the stock on them is Quick Detach, you can turn one into a 16" barreled pistol in seconds, with all the available advantages of a rifle if you want it. As light as they are, I can't see you having any trouble with the weight.