That depends. I have driven my MINI on stock 16" X-lites with runflats and with R90 replicas running conventional tyres. The ride is noticeably better on the 17s.

They look better too, and the R90 replicas/regular tyres weigh less than the OEM 16" wheel/run flat tyre combo too before the next person pipes up with the usual critical comment in the 16" v 17" discussion.
Cheers Liam