[REAL 1]

No doubt the 17" tires will perform better then old technology bias ply BBs.
The 15s will ride nicer.

I have BBs on mine. They need time to warm up. Cold,they feel greasy. Once warm they are fine but they hunt and track all the little imperfections in the road. You get used to it. I have had no problem with flat spotting over the winter but I increase the pressure to about 40 lbs during winter hibernation. Note they are NOT DOT approved.

BB are definitely the correct Cobra look.