Depends upon your mission. How much do you want to carry? Do you want to travel a great distance? Do you want to travel a great distance with a woman?
If you can travel with a sane load the KLR should do fine. If you need the kitchen sink then the load ability of the GS might fit you better.
Both are fine machines and have traveled most of the planet.
What is your ability? A light KLR is less in need of skill than a loaded GS on loose terain.
I have one of each and each has is use. For me if I had to have one it would be the GS for sure.
One thing to keep in mind is the KLR will depreciate, while the airhread should only appreaciate from here on out