[Aussie Mike]

There's a good range of performance tyres available for 17" and 18" wheels compared to 15" (down here in Australia at least).

The larger rims also open up more options for brakes too. I've got 17" rims and I'm in the process of fitting some 13.5" front rotors and 6 piston calipers on the front and 12.9" rotors on the rear with 4 piston calipers.

It depends on whether you are after performance or original looks. The 15" tyres and rims look great and really fill up the guards but the right choice of 17"or 18" rim and tyre can look great too.

Cheers