Some may disagree with me, but I believe the difference in net effect of sub q vs im is essentially unrecognizable for most people. i would think that ease of injection would generally matter more. Basically, the only difference between sub q and im is depth of penetration of the needle. I'm very, very lean, so any quad injections are going to be IM by necessity. If it's important to you to ensure that you're only injecting sub q, i would pick a spot where you have a fair amount of fat/skin to pinch.