Do 18" rims really slow you down?

why doesn't steeda have an 18 x 10 option on their ultralites.......amnit: that would solve the weight issue and give you the looks in return...on the '05 saleens s/c'd the stock wheel is a 20" and the option is 19"....yes 19" is the option wheel....5.0 magazine stated after testing this car that, and I qoute:"To boil all that down, if looks are the main attraction, go for the 20 inch rolling stock. If performance-or ride-is the key, the 19s are the answer." Now this is vehicle specific but I'm sure the same applies when 17 to 18 inch options are concerned.