Well I'm too much of a novice to say that I notice much of a difference. But the Zurich has set PR for time on standard 20 and 24 mile routes I ride routinely. I still seem to pick the Circuit more than the Zurich though because the Circuit's fit does my bad knees well. I've emulated the fit as best I can on the Zurich but just can't get it right for the knees. Really jacked up my right one about two weeks ago (I've been putting off surgery on the meniscus since April) and while it does not hurt biking and really aches the rest of the time. But the circuit is down for repairs on the rear wheel after being clipped but a truck a couple of weeks ago so the Zurich is all I 've got functioning right now.