If I'm jerking off with someone: fat cocks are interesting, and really fat uncut ones are the best providing they are long enough to get a really good grip going.
But, if I'm trying to give a blow-job then, small thin dicks are the best, or long and thin...but, I don't like to deep-throat...I have sensitive gag-reflexes.
On the other hand, because i have a really long one, at the bath-house there are always guys that want me to fuck them....so length must feel good...at least to some people. I have never been fucked myself...my butt is just too small...so I'm only going by what guys tell me to do to THEM.
However, I do love jerking off with guys with really fat dicks.