A few months ago I tried a 15 model GS to compare to my early 14 GS, and decided that the gearbox wasn't really any different. Yesterday though, I had a new R1200R loaner and the gearbox on that was absolutely lovely. Definitely better than either GS I've ridden. Even the GSAP slid in effortlessly, unlike on my GS which needs a firm prod a lot of the time.
I tried the new RS and the gearbox on that was as good as my TC no clunk into first and the quickshifter was seamless .
But why so different !