Having just left a 2018 Goldwing Tour for a 22 R1250RT I can offer a redneck review of the differences. The 200 pound weight loss is appreciated. RT is easier to do low speed maneuvering on. I really enjoyed the Wing for 62,000 miles but it just started to get heavier over the last year. If Honda made a 600 pound Goldwing I would probably still be on one.
Thinking maintenance on the RT will be easier. After changing the air filter on the Wing I decided to trade versus doing it again.

Valve checks are fairly easy on the Wing. Shims for the intake, screw and locknut for the exhaust. I did have to adjust several exhaust settings but no adjustment needed on the intake.
Haven't had to check anything on the RT but will have to source some additional tools. Looks easy enough to do on Youtube. Doesn't it always?
One advantage I miss from the Wing are the backlit switchgear at night. RT does not have backlit controls so you have to get comfortable with feel in the dark. Hasn't really been a problem, just a learning curve.
Rear tire change requires removing the RT muffler to get room for the wheel to be removed. Wing required removing a rear panel and support bracket to get the wheel out. Installing the Wing rear back on is not the easiest to get the wheel in position. Thanks to Uncle Phil on the air bladders for wheel positioning. Should have done that long ago.
Wing speedometer was spot on the money. RT is off by 4/5 mph. 80 indicated is actual 76. Wing is tough on front brake pads. RT remains to be seen.
Cruise is better on the Wing. Disengage is very smooth. RT not so much but it does have the adaptive cruise which I find works better on the bike than in the car. Go figure.
Four years on the Wing and it was time for something different.
Honda regular gas vs RT premium.
A big plus has been quizzing Mellow on add on stuff for the RT. He is killing my pocketbook.
I have over 200,000 miles on BMW's, mostly older K100RS. Never left me on the side of the road. Hope that remains the same.