Hi
I bought an R and enjoyed it so much on tarmac that I bought a X.
Didn't like the X. Too responsive and too uncomfortable (for me) so sold it and still ride and love the R (99.9% tarmac)

I would like to try a Z, but like a lot of others here, I have a transalp which although not exciting, is dependable.

Re the X and comfort... I found the seat too narrow and the bars too viby.

Rob