1250RS is not top of the line for sure in any of the segments it is marketed at. I would say a K16 would be more towards the top.
Top of the line, in it's class. A sports bike, with shaft drive, linked brakes, traction control, and heated grips.
Find me an electric bike with those features for anywhere near a comparable price. Specifically, I will not even consider a bike without a shaft drive (or in the case of an electric, a hub drive would be acceptable.) I am done maintaining chains and belts.
Now if you look at K16 specs, 160 horses at 6750 rpm with 123.7 lbs-ft at 5250 rpm. And it DOES have linked brakes, traction control, ABS and heated grips.
Both R1250RT and K16 are marketed in the sports tourer segment.
So NO, R1250RT is no where near top of line sports tourer and definitely not a sports bike.
The disadvantages of belts are efficiency (especially compared to chains), off road durability and trailside serviceability.
My bike has been rock-fucking-solid. Its been in the shop once for a real break in 16 years for a busted fuel line. (not including tires and engine oil changes). Its really hard for me to believe another bike could be as reliable.
On an R1200/R1250 it's 12,000 miles or 2 years.