Autocross/Road Course driving on 15" wheels. What's your experience?

I'm also interested in this topic as this is something I'm contemplating (I like the look of the old/older school 15" wheels/tires combo), but if autocross is something I'm into I think the answer is large rims and lower profile tires with stiff sidewalls (there is also more sticker tire options with 17/18" wheels). I think the answer may be keep the 15's for the look and swap for larger rims with stickier tires at the track for performance, but I'll await the more experienced member to chime in.