Seems to me that the GS and RT are a little too similar to justify owning both bikes. I’m amazed by the number of people on here who own both. Whilst I appreciate that the RT is a great bike, I’d only consider owning one if I sold my current 1150.
I’ve never ridden an RT but what exactly does it do that a GS with an aftermarket screen and comfy seat doesn’t?
I have both

Quite different.....................for a start the RT has more HP (1100 RT = 90HP v 1100GS = 80HP and 1150RT = 95HP v 1150GS = 85HP)
Power delivery is not the same either
That makes it able to attain a higher overall cruising speed
Against a stock GS, a RT has a bigger tank range, making it go further without refuelling. This means that less fuel stops per day equals a greater distance covered in a touring day
Having a fairing means that you can cruise 10-15mph higher on average all day than you can on a GS
Less windblast because of the fairing means you don't get as tired as you do riding a GS
The electric screen is a huge bonus, compared to any aftermarket GS screen
Having a fairing means you stay cleaner on a RT than you do on a GS
I rode last week in heavy rain, in jeans and trainers ( I know....ATTGATT) and I stayed 100% dry..................try that on a GS, you'd be soaked
RT and GS's are more different than they are similar................end of
on the 1100's, which is a plus - just normal regular ABS2