Horse power to weigh ratio. I bought a new BMW F650GS in 2007 and rode to Tierra Del Fuego from the USA. That bike is single cylinder, chain drive, tube tire machine that gets 25km per litre, 62 mpg, at 100 kmh day in and day out. It has a 400 km range with no extra tank needed. It comes with heated grips, abs, and a good saddle. I rode it stock, including the chain. 52 hp, single disc brake, 380 lbs +/-.
In 2011 I bought a used BMW F800GS. I am short ( 30 inch inseam) so I lowered it myself. Had all the cool stuff on it. After 5000 miles I had a tank slapper wobble at 75 mph on the flattest, straightest, smoothest piece of asphalt in the world on the interstate at Lexington, Nebraska and destroyed the bike. I survived because the bike had crash bars and I wear all the gear all the time. The next day I went to the see the bike. It started right up and was rideable - barely. I had bent the frame - so I junked the bike. It was smooth, got 50-54 mph (so not good for RTW distance), stock saddle was comfy! I do not know what caused the wobble. It could have been the knobbies in wind. It could have been wind shear. It does not matter now.
I have purchased a new 2013 factory lowered F800GS. It arrives here shortly. I have kept my old F650GS single. They take money to maintain - but I am emotionally attached to a pile of metal and rubber. The F800 bare is 82 Hp, 415+ lbs. So I have voted with my pocket book. It still amazes me that I rode 18K miles to Ushuia Argentina without a scratch, but got dumped in Nebraska 5 miles from a hospital.
I live by these rules on adventure travel. Simple is best. One gets exactly what one pays for. I saw a lot of Honda transalps in Argentina because the rental agency rents transalps. Lots of BMW's in Chile, because they have a dealer in Santiago and the tour companies all use BMW. One should look to see what bikes the tour companies use for their guests. My observation is that BMW is used because they are durable and dependable.
My BMW's have broken from time to time. And I am not always happy with service or dealers. But the fact is that the bikes are tested, reliable, and German. Nuff' said.