15" does limit the choices. I ran 16" and was very happy with my Compomotive wheels. 16 looks pretty close to 15 visually and allowed more choices.
Also my wheels were "bolt on". Important to me because I DID change wheels with pre-mounted tires for some track events. 16" bolt on Ford rims are VERY easy to come by! I'd hate to buy a second set of "pin drive" wheels just to have around for "racing"!
Ernie