I just rented a '14 GSA in Tuscany and put 500 miles on it. The power advantage is significant over the S10. I've always thought these bikes felt huge when I sat on them in the dealership. After a few days this was a non-issue. Overall it was an exceptional experience. The handling was excellent and the bike felt light. I came away FAR more impressed than I expected to be.
That said, I couldn't live with those damn cylinder jugs poking out the sides. I'm 6'2 and pumped my shins on them frequently. When I got home I immediately got on my S10 for a ride to compare and it just fit me so much better. I'm also in love with Yamaha quality and own 3 to prove it. I'm hoping in a few years Yamaha will add some significant power to the S10, and if they do I may end up consolidating my FJR and S10 to the new bike.
That said, I couldn't live with those damn cylinder jugs poking out the sides. I'm 6'2 and pumped my shins on them frequently. When I got home I immediately got on my S10 for a ride to compare and it just fit me so much better. I'm also in love with Yamaha quality and own 3 to prove it. I'm hoping in a few years Yamaha will add some significant power to the S10, and if they do I may end up consolidating my FJR and S10 to the new bike.