Is there any significant performance difference/handling between the 15" vs. the 16" aluminum alloy wheel? Picking up my new Mazda 3GS 15" aluminium wheel this weekend and considering the upgrade to the sport pkg (moonroof, 16" wheel). Do not really want the moonroof, but wondering if I will regret not getting the larger sized wheel. I am not concerned with looks, only with handling. Would appreciate very much any input from mazda owners. I am buying the car from a dealer 300 miles away from my home and cannot test drive both sizes (only test drove a 16" with the local dealer)...he knows I am not buying from him and therefore he won't want to waste time letting me test drive a 15" which I am scheduled to buy at the moment.