Guys I'm going to be pretty brutal here. Serious tip....size
does count. That thing about size not mattering is what we tell guys to spare their feelings.
If its thin then its not going to stimulate us very much at all. And a longer one keeps the action more continuous and sustained. So fairly long (6+ inches I guess) and good thickness (maybe 5+ inches around) combined makes for a good tool.
But then you still gotta know how to use it.