Hard to beat... so you're saying you like the QC-10 better? Can you slap any 9mm upper on the QC-10 lower?
In terms of aesthetics, yes, hard to beat. Functionality, there really isn’t a difference. Any 9mm upper will bolt onto it. I believe Quarter Circle is out of business though so finding one of their lowers may be difficult.
"But when it's time to fight, you fight like you are the third monkey on the ramp to Noah's Ark; and brother, it's startin' to rain."