People who go with a slightly taller tire, 55 series instead of 50, seem to feel that the bike turns in better. That would seem to make sense to me, with the somewhat rounder cross-section. As an extension of that theory, it seems like going wider would adversely affect the bike's excellent handling. The contact patch being such a small part of the overall size of any bike tire, I don't think that traction is going to improve much. So my thinking is, if esthetics is a priority over performance, go for broke. Like some others have said before me, I go with stock sizing exclusively.
How come nobody ever wants to put a huge tire up front? 230's front and rear, now you've got something unique!