Exactly, the suspension dictates the behaviour of the car over bumps, the aspect ratio of the tires will translate more or less of the surface characteristics. The differences are subtle.
I believe the X-Lites are an S only option. You got yours as take-offs, so you're lucky.
I would prefer non-run-flats on a Cooper, if it was equipped with a spare. The lower weight and lower rolling resistance would eventually save money on fuel. All MINI's have the low-tire-pressure warning light, so the most common reason for tire failure is already drastically reduced - over or under tire inflation.

Chilli Red/White Cooper S, Sport Pack & Sunroof. Delivered June 12th, 2002!
Now with MCS Winter Tire Package.