I have the mirror wind deflectors and the side fairing wind deflectors.
The mirror deflectors are only for looks because I have 3" Roxx Risers on the handlebars. Some people fit motorcross style hand protectors to the handgrips for better wind/rain protection.
I have always liked the side fairing wind deflectors. The benefit for me was to stop half of each leg from getting wet in the rain, but I like the way they make the bike look as well. I got all of the deflectors from DSS.
Rodd