The OP asked a very specific question, not KTM vs. BMW or any other question, jeez, the opinions one gets on this site.
the difference was all about the gas tank capacity and not much else. I love the huge tank and the comfort it gives me knowing I have enough fuel. It changes the way I plan my trips and ride. A great deal of my riding is in Baja where gas availability is always an issue but even in the states its great not having to worry about fuel.
btw- I had a 950 Adv and loved it but it did not accomodate my sweetheart on the back very well. (Note my Avatar, that's her on the back of the 950 somewhere on the beach in Baja). We took a trip to New Zealand and rented a GS, and loved it for that road trip. When we returned home I sold the 950 and bought the GSA. I love that bike.