I ride enduro and trials and get the dirt bike magazines. Dirt Bike magazine started an adventure bike section a while ago and has a tenere vs the new water cooled GS in the December issue. Looks like most of the December stuff isn't online yet. Their take; the one area the Yamaha has the edge is when you take to the dirt with the various electronic ninnies disabled, the Yamaha feels more natural and handles more like a dirt bike.
http://www.dirtbikemagazine.com/ME2/Default.asp
http://www.dirtbikemagazine.com/ME2/Default.asp