Just depends on what you want out of the car I supose, the Focus RS is aimed more at performance. Where the Focus ST is a mixture of performance and comfort and is a bigger the car, and i'm sure is the heavier as well with all it's computers and extra safety gear.

I just love the way people stop and stare when you drive past, and it's not just the boy racers either my wife said she saw a bloke in a 6 series BMW having a look as he drove past, then slam on his brakes as he near hit the car in front of him