FYI...not gonna name any names....BUT there is a guy here trying to give advice about pinning when he just started a forum about wanting to do his first cycle...
With that being said, I prefer the quads with an insulin needle... I don't really get any PIP. Also, don't have to twist my body awkwardly to pin the glutes. Will I pin the glutes? yes. But quads are my favorites.
The quads have a lot of veins. So if you aren't lean enough to see them, the glutes might be a safer route.
Everybody has their preference. I don't mind the delts either.
I like the comfort of being able so comfortably sit and do my injections.