They are both great bikes. It really comes down to your preference and the need to be honest about how you are really going to ride them. If you’re just doing dirt roads and touring then the GSA is a great machine. If you’re really going to off-road it, then you’ll need to be strong enough to pull it out of mud holes and pick it up 10x a ride. So taller people with a fair amount strength do better on the GSA in a true off-road situation.
You should test ride them both and decide which is more comfortable for the type of riding you are doing.
Also, there’s a lot of room between the $6500 2007 and a $27k new bike. Any of them can be setup to your liking. If you are taller then one of the older GSA’s is definitely a good buy. If not, then any of the GS’s will work. We have people riding anything from the older R1100GS’s to the new R1250GSA with us. The 2006-’12/’13 oil heads are great bikes for the budget conscious, or if you really plan on beating it up off-road. They will need engine crash bars and I would recommend a Black Dog skid plate on those years to prevent crankcase damage from the OE mounting points.
You may find that you really just prefer the dirt/seasonal roads and the any bike, with just about any tire will work. If you’re going to ride Michigan sand then a TKC, Shinko 804/805 or other big block tire is really recommended. An 80/20 tire won’t work well unless you are very skilled off-road. If you’re a beginner then the big blocks tires will be more enjoyable and safer. Tires are cheap and easy to change, so I would not make them part of the consideration.
Best of luck with your search!