I've always prefered the bigger raids. In WoW, I was a member of a 25m raiding guild, and the mayhem and chaos of trying to get 25 individuals to work as a team is really as much fun as it gets for me. In SWTOR, I've only experienced 8m ops, sadly. I've been a member of 2 raiding guilds, and experience taught it was hard enough already to get 8m together to raid, 16m was completely impossible.
Recently my second raid guild died, and even though I love the game, I've given up and unsubbed. I just don't relish the thought of applying to and settling in with yet another guild, only to watch it go downhill again. I've participated in all the ops (HM) up to but not including TFB, as my guild went inactive shortly before the patch. I've consoled myself with the thought that I've seen and experienced most of the game
A proper 16m raiding guild might make me reconsider and sub again, though!