I've got an'04 1150 GS and have not ridden an RT yet; therefore, my response may or my not be of much help. I'm 63 with a 32" inseam and have ridden my GS 50,000 miles mostly on long cross country trips; best was 9,000 mile trip to Seattle and back home to Tennessee.
Originally Posted by striders
I love my GS; best motorcycle I've owned-had 7 since 17. It is pretty heavy, 560 lbs (1200 is 50 lbs lighter), and tall (1200 is a tad lower). Because of the weight and height I've dropped it at least a dozen times, virtually all at or near a standstill. Other than twice breaking a turn signal lens (always left side) it doesn't get hurt as I have cylinder protection bars and always ride with system cases attached. On level surfaces picking it up is never a problem, but once I dropped it in heavy gravel on a steep hill and it was a real chore to right it.
It is a very comfortable bike for really long rides. On my 10 day trip to Seattle I averaged ~500 miles/day, longest was 630 miles. After reaching Santa Fe all of the roads were beautiful back country roads. It rides well on interstate highways, back roads and gravel or dirt roads, and corners better than any bike I've ever ridden. I use a Throttlemeister throttle lock, aftermarket handle bars, which moves position up and back, and a BackUp backrest to make life easier. The original windscreen sucks above 50 mph!!!! I went through several iterations before finding an acceptable solution--I use the GS Adventure screen with Torbinators. I've never replaced the seat as I've always found the stock seat to be adequately comfortable. My friends have told me I've obviously got a "BMW butt". Although I try to avoid riding after dusk (too many deer) I found night time illumination to be inadequate and added PIAA driving lights.
I do my own maintenance and repairs and have found the GS to be as easy to work on as my former BMWs (R90/6 and R80/7) with the exception of changing tires alone (is royal PITA due to rim depth).