Smaller bars are for more of a tech style I believe. Because it makes allot of the tech tricks allot easier. Unlike the larger bars which is for more of a style rider. Because turndowns, look backs, tucks, ect look allot better and are easier (I believe).
But, I ride 15.5 because im more of a tech rider, and tend to throw bar spins more than the average rider. Although I wanna maybe move up 16s or 16 and a half?