handling car 17's or 15's?

too keep it simple i went with 17x8 and 245 45 17 on all 4. kyb shocks, 920 t bars but have 1" for when i go form s6 to bb. hellwig sway bar frame connectors 6 leaf espo springs, with nylon front eye bushings and prothane hd rear shackles with poly bushings. im still running the original rubber and joints in the front but it handles nice. ride quality is good. the tires are stock size for mustang so its not like they are super lo profile. handles bumps fine but still try not to smash them. i never bothered to figure it out but they are about 4.5" of rubber, probably pretty close to the stock 13 or 14" tires. there are still some ok tires in 15s but i dont like what is available for front sizes and its hard to find the same tire for front and rear. the 17s with all that backspacing fit nicely over the 11 3/4" rotors and calipers. i dont think you could do that with 15s they would be much closer to the fenders. my front and rear track width are pretty close with this setup. i alway thought they looked wierd with the front track wider than the back. im not sure how that effects handling.