While glutes are damn awkward, they're still my favorite because I hate risking any impingement on my arms or legs that will keep me out of the gym for even a day. My body always seems to "know" that I've injected, meaning I do feel them for a couple days, so I like to have it somewhere I can tolerate.
Also, frankly I don't know enough about the nerves and vascularity in places like my calves to feel confident injecting there.
But in reality, for me it is not about a favorite, because it is not wise hitting the same place over and over so basically I do a number of locations ... favorite or not.