Two different animals.
I tested the HS a couple days ago! We ride mostly in the city with traffic. You can move the bike like a bicycle and switch lanes without a problem. It's a slim bike and you have no problem maneuvering the bike.
I did not had the chance to get off road but I'm sure it can handle some very light dirt roads.
I felt the bike very good and, yes, you can't take the sime out of your face when you ride the HS.
Test #2. BMW F800GSA.
This is a big, heavy dirt bike. While riding in the city, you will struggle to switch lanes and get ahead of the traffic. But once you get out of town is a very different story.
Very comfortable in the roads, highway, and is can take almost any dirt road. Still very heavy to do some serious enduro, but it is very, very good.
I felt the bmw more comfortable if you are going to do long trips and get into dirt roads, but in the other hand the HS is a blast arround the city.
The HS has more power, throttle response and way more less vibration at high speeds than the F800GSA.
The BMW has more wind protection, but you start feeling some vibration in the foot pegs at 65+ mph.
My final thoughts are.
HS - best bike to commute arround the city, great for short trips, extremely fun bike.
F800GSA - best for longer trips, good on and off road, best for 2 up.
There is no way to compare this bikes, both are good for their purpose and all comes down to what you are going to do with the bike.