I have a DL650 and my fiance has an F650GS that I occasionally ride. We've only been riding for about 4 months and don't have any off-road experience.
manuvering the two around the garage and the drive, the BMW feels more nimble. It definately has a shorter turning radius if you can turn the handlbars full lock.
On the go, I much prefer the feel of the V Strom. with some foreward movement, it feels more stable to me. From an acceleration thing, the VStrom seems more quick to me, but if you get the BMW up in the 4,000+ rpm range it'll keep up just fine.
You really need to sit on both and see how they fit your body style. Both my fiance and I have the same inseem, but I can flatfoot the V-Strom and she can't. But she can on the BMW, which has a more narrow profile. On the other hand, the VStrom controls seem just right for me, but sitting on the BMW it feels like I'm right against the handlebars. The only way that I can make a full lock turn at slow speeds is to move my ass all the way to the back of the seat to make room for the handlebars and my elbows.