I like the old Boxer engines best. Forget what they did in 2010 to make them less desirable, but I’m sure there was a good reason here. Thinking a GS would be best for the riding position, but I also really like the 1100S. Either way, I really don’t want a super high mileage one. Why the 2009 or older? I believe they want to shimming valves in 2010 vs. screw-type adjusters and if I’m going to get one, I may as well have the easy maintenance.
Here’s a pic of an R1100S:
And an R1150GS: