Vocabulary is often mentioned, and sentence phrasing in general - this being due to the likelihood that a stutterer will attempt multiple routes of words when speaking, to arrive at what will give the least amount of problems. Of course, it's not necessarily an "advantage" in the short term sense, if it acts as a cognitive burden (and in a sense, is just a bunch of _escape_ routes). Also, I think stutterers tend to be good at identifying other stutterers, but I'm no sure that's a benefit as such? It's like a side effect, I guess.