I have driven an STi but definitely not a Carrera S!!! The STi like an Evo is quick out of the box and very easy to drive fast. From what I been told, it's not as easy to just jump in a Carrera and drive quickly. Sure you could just stomp the gas to the floor, but taking corners quickly will take some getting used to - the rear engine, rear wheel drive layout can make the front-end feel 'light' at times.
Glad you got to drive a Carrera S! What model year was it? I'm jealous.
-Chike