Tricky question.....I only know I sold my naish GT 9'10 (it was thrashed almost to death) really cheap to someone......explained that it was better to get a paddle with the tuff shaft even though apparently an expensive choice.....rather than buying and snapping two cheap paddles. But some people ask for advice but don't want to hear the answer lol
Yep xTuf (s) (s is for stiff I believe) is definitely stiffer than the xTuf but still has a decent amount of flex.
I have both but prefer the xtuf (s) for racing, downwinding and use the xtuff for surfing.
In order of most to least flex for KeNalu shafts it goes xtuf, xtuf (s), Elite 90, Elite 100.
For me in my 50's with I find the 90 and 100 a bit hard on my shoulders.
90 and 100 refer to what KeNalu call the KeNalu flex index (KFI)
the xtuf is the equivelant of 60KFI and the xtuf (s) is 70KFI
I have now had my original xtuf (s) for a couple of years it has had hundreds of hours of downwinding and surfing.
Several flights international and national, bounced around in trailers, boats and on coral reefs in Indo etc and is still going strong, love it.