I drove both models as well, my friend has Versys, and I made about 1000 kilometers on it. If You'll ride alone, it's not so bad, even it's not suited for more than 300 km a day, because of it's unconfortable seat for such a long trip. Especially it's valuable info for person behind You, for pillion Versys is very unconfortable.
As regarding GS, it's my favourite, because it's still BMW, and it's worth of every damn penny You pay for it. For driver and pillion, it's unmeasurable much confortable than Versys, has more fine line of power and torque, less undesired reactions. Versys is faster and stronger, but BMW is BMW, especially when You wants to sell it. And quality is strong ace of BMW.
Picking between Versys and F 650 GS depends on Your needs, especially do You ride alone or with pillion. For pillion, longer trips, confort, quality and image - pick BMW. For ride alone, power, top speed - pick Kawa.