I asked this very question a while back about Muni sizes. The Forum has this not well known feature where you can create a poll and see the results that’s what I did here:
Because of the polling results I decided to get a 27.5 Oracle and I think it was the right choice for me. Of course I was asking about muni-specifically, I think I would have opted for a 29 if I was going to be doing primarily Road riding.
It might be interesting to create another poll specifically for Road riding sizes to see what people’s votes turn out to be for that style…