glutes definately. less veins to worry about i would imagine too.

I prefer the thigh, much easier to control whats going on

Delts... Less pain and quicker recovery it seems. When I hit my thigh, I can't do squats or cardio (run/jog) because it throbs.

Quads. Unlike others I have never had a problem with them in terms of hitting nerves or excessive bleeding. Plus they are the most easily assessible muscle group to inject. I wish I could do all of my injections in my quads.

...I agree, and it`s very difficult to self inject in the ass against self-injecting in a thigh. When injecting in a thigh you can stay relaxed seated and doing everything slowly !