Actually it makes a big difference, and not just about scar tissue. There was a study done that showed that injecting Nandrolones in the delts caused lower blood serum levels than injections done in the glutes. Probably due to being a larger muscle group and having better blood flow to the muscle. So technically, glutes>delts.
With that being said, I still rotate to delts just for the sake of convenience. Glutes, delts, quads is my standard rotation. I just go around the body in a circular clockwise rotation. Makes things easy, and keeps injection sites fresh.