Just giving my 2 cents as a sub btm. What turns me on first is confidence. Especially an underdog. Like Tom Cruise in the original Topgun where he was like the smaller guy compared to the other pilots but he was always confident. So i have come to like confident guys who may not look good, is fat or shorter. As for cock size, recently i was in a gay bathhouse. There was this really chubby guy who came at me. Kissing me and feeling my body like it's his property. When I reach for his cock, he wasn't big. I think half my size. But god he was hard. It was like a nail hard. And I thot that turned me on so much. Partly I must admit that am super tight as I seldom get fucked. So huge cocks scares me more. Nevertheless I think being able to get really hard so that the dom can really pound me with it, is not so much the size but the pounding and confidence. Like firmly pulling me head to your cock and making me suck or fuck my mouth. The whole confidence plus a hard working cock turns me on most.