"Eating gravel road like there's no tomorrow?" Those words are like from a poet's mouth
Here in Estonia we have alot of gravel roads, almost half of the roads and the tarmac is often worse than you can find in the third world. You can brake your own teeth riding a sportsbike on our main roads...
Typical hot estonian summer dirt road with the speed:
What i like about the GS is the stability, i haven't yet tried any other big trailie that feels so planted on the road on the high speeds. I don't know if it's the boxer engine or the telelever causing that keeps it so balanced on the very high dirt speeds, or it's the symbiosis of both.
I do about half of my ridings on gravel and dirt. Using the bike every day as communiting, long weekend rides and travels. Can't say the paralevel is unreliable at all since i got in these bad conditions 50Ks on current and 60Ks on previous bike with no problems with it and acctually no probles at all with the bikes. Indeed, on travels i carry spare final drive bearing, seal and shims with me, they take very little room and don't cost much in case of a FD failure. But that hasn't happened yet.
I think why BMW went over to paralever was the ellimination of the lift-effect and weight issue of the shaft drive. With 2 connections (typical swingarm) you need 2 additional torque arms to elliminate the forces symmetrically from the lift-effect the shaft drive creates, and that means more weight, more details. So the paralever was chosen to make bike lighter and better handling by doing it from one side only, 2-times less details and the same strenght just using a larger diameter "pipe". Some argue that the 1-connection to wheel puts too much stress on the bearing and referring to failures, but others say physically it's on the same way balanced as with a 2 connections and you see HP2 do 20 metres off jumps and R900RR have raced in in the Dakar successfully, also the famous HPN-racing prefers this system altough they only tune the older airheads. And now finally Moto Guzzi has copied the idea of paralever to their new generation bikes. So looks like there really is a serious reason why this system was chosen altough some say it's a solution to a problem that never existed.
I'm the owner of 2nd '98 GS 1100, first one written off in Poland, but since it was so good i got another one.
But i imagine any of them will do, airhead or oilhead. If you're aiming for 1100, get the '97-'99 models, not earlier that have some known issues if planning over 100K mileages. Some even argue those late 1100 models are the most ironed out GSes ever made, don't know if it's true or not.
R11xxGSes are pretty simple bikes accually despite lot of people think they're complicated. They're not! Any bike you get, buy the Clymer or Haynes manual to start working on the bike your own, it's the best way to start learning your bike's technical side, lot of additional know-how and tricks go around the internet (forums) too.
Hope this helps!