I notice a definite change in ride quality when I put new tires on, even when replacing like for like. I tried climbing a big mountain in Gatorskins and wished I had GP4000s on instead, but I also wished I had my own bike instead of the rental (it was a very nice rental, about equivalent to my own, but still not my own).

I've had some other tires on my regular road bike over the years and always regretted not just using the Conti 4000s.