Comfort is not my biggest issue. It's reliability.
1990 BMW R100GS Paris Dakar model. PERIOD.
Not the prettiest, not the fastest. Decently comfortable. But most importantly, absolutely bulletproof!!! They are simple to maintain, will run forever with serious neglect and minimal service.
I had an '89, pre-PD model, so it only had a 6 gallon tank. The Paris Dakar has a 9 gallon tank. The PD's also have a bit more windscreen, so you don't get quite as buffeted at speed.
I got mine with 77K miles on it, and sold it 6 years later with over 400K on it! The damn thing just keeps running. Think of it as the "B-17 Bomber" of the motorcycle world. Not pretty or fast, but will take a serious beating, and get you home again.
And they're decently priced for a solid one... $5000 is the median price.
If the GS is a tad on the tall side, try to find an RS model. It runs a 17", instead of a 21" front wheel. Both use a 17" rear. Oh, and don't let the spokes fool ya, they're tubeless!!! But carry a spare tube, just incase.
Both run a disk front, drum rear brake set up. The rear is a cable operated, and fronts are older Brembo hydraulics...still damn fine units. Clutch is a cable instead of hydraulic. I would suggest getting a second clutch cable, putting a few drops of lube in the housing, and taping the ends closed. Zip tie it in line with the existing cable. If you snap a cable, then all you have to do is peel the tape, and swap the new one in. It's one of the very few weak links with the air-cooled BMW's.
Unless you absolutely destroy the motor, most repairs can be done roadside with a few basic tools. Heck, if you're really in a bind, even an old VW shop can work on it!!! It's the same design as the old beetles, minus 2 cylinders.
The factory seat is fine, even on loooooooooooonnnnnnnggggg rides. The only thing I ever changed was the bars. I swapped out for a pair of R1100GS bars. They're a 3 piece design, that has vibration dampening inserts that run the entire length of the grip area. MAKES A HUGE DIFFERENCE!!! Oh, and skip the throttle lock doo-hickies, and just get ya one of those $6 "Cramp Busters" plastic thingies that slips around the throttle grip. Easy to use, and still allows the throttle grip to rotate if you loosen your grip/take your hand off. Just a tad safer, IMO.
I can't say enough about the durability of the GS series. I would stick with any of the R100GS models between 1989-1995. They were all carb'd...no fuel injection/ECU to worry about. If you trash a starter motor...some had outstanding Bosch units, and others had some crappy French turd that always died...you can go to the local pick-n-pull wrecker yard and get the starter motor from a '99 Saturn. Yes, a Saturn car. It bolts right in!!!
I love my Ducati, and would never think of ever replacing it. But if I had to choose one bike to use as a do-all, go anywhere, ride through the Apocalypse machine, then the R100GS is the one and only way to go!
I'll stop now. I could go on and on...obviously.
Check out
http://micapeak.com/bmw/gs/It's probably the most comprehensive assembly of information on the entire breed.
Good luck!