I run 18" simply because the tires and wheels are cheaper and the sidewall is more compliant on an 18" tire. Next time I will get the 305/45-18 vs the 305/35-18 I have now because of the height difference. The transmission sometimes gets confused because the wheel speed is different than the indicated speed and I don't have a tune to compensate for the tire swap.
'15 Z/28 #325 black a/c & stereo. 2:10.9 VIR Full 1:44.74 Summit Point Shenandoah Circuit
Advanced Induction cylinder heads & B-3 cam (RPM) ARH 1 7/8" headers, MSD atomic air force intake. 575rwhp/500rwtq (conservative tune).
'12 ZL1 10.52@131 1.55 60' 2:13 VIR Full (sold)