Give me two guys exactly the same in every way, say I have no feelings for either of them, I don't know them in the least, but I have to have sex with one of them, but one of them has a large penis and the other small, nine times out of ten I will pick the hung guy over his lil doppelganger! I only say nine times out of ten because after choosing his fat cocked twin to bang the lights out of me nine times, I would probably start to take pity on his lil other and decide to send him home not completely empty handed, but not before I got my nine bangs from captain fat cock first, he's going to have to deal with sloppy tenths! lolol
Unless it was my first time and I was intimidated by his size (Which I'm obviously not.), I can promise you that's what I would choose.
Basically, size does matter, but only if other things don't matter more. That's my opinion.