For a road bike, the belt is a great thing. For a bike meant for roads and unpaved roads, (I don't see the V-strom as a single track machine - what you do with yours is up to you...) the belt is probably the worst possible choice.
Yes the belts can last up to 120,000 miles, and they are very low maintenance. But the 1 thing that will kill a $3-400 belt in seconds is a small rock or gravel that gets wedged between the belt and the pulley and splits the belt. Most times it's GAME OVER.
So that's why its a bad choice for a dual sport.
As for chains, I understand that with regular cleaning and lube with a dry Teflon lube like DuPont chain saver, people are getting 40,000 miles out of their chains.
I always thought that shaft drive was pretty great, but BMW and the Suzuki C50 disabused me of those notions. So all things considered and for the type of machine the DL-650 is. the chain is the way to go.
15 DL-650 Metallic Triton Blue ABS
14 Vulcan 900 Classic