The GSA is a fantastic machine. I've owned 2. If you are a guy who likes to accelerate, it may not be a great choice compared to the gtl.
I know, I know, the GSA makes plenty of power for it's intended use, but I would have preferred 25 more ponies.
There is a water cooled GS coming out and it should make more beans....
I bet a GSA could beat a gtl though, in the twisties. Until the corner exits.
Passenger comfort? Get an Ultra.