I haven't ridden an s but it was a serious option for me at the time.
the R has a higher ground clearance and check how hard the suspension is on the S. Also check the ride height, I think the s saddle is slightly taller

even for road use I find the compliant suspension of the R excellent for dealing with potholes and bad road repairs and rumble strips!
the 21" front is cumbersome but is more useful for climbing kerbs and obstacles

this is what I cinsidered when looking at XT the rest is really your preference and use