That is a tough choice. BMW makes a nice bike, and their owners brag about how great they are to ride. The GS is the most interesting BMW to me. On the other hand, if you were headed on a trip...for example, Alaska as you mentioned...Asian brands have a much better dealer network, as well as the parts being cheaper. Consider that for the cost of a used GS, you could likely buy a new Wee-strom and end up with a full warranty, or buy a lightly used one you could get an extended warranty for, for half as much.
I think you would be quite happy with the GS as long as it doesn't end up having final drive issues...those can get quite costly.