Owned a F800GS. Own a 990ADV R.
I rode the 800 pretty hard, dropped it quite a bit...still a heavy bitch...not a dirt bike. Soooo, if you are going for a heavy big bike anyway...990 no question. I did love the BMW, thought I was going to get another after I wrecked it. I am sure I made the right decision going to KTM now though. Try it out dude, if you hate it (not going to happen) you can always sell her and go back to the 800. 990 makes smiles everytime you get on it, and sounds way more badass when you get a real exhaust on it.
Of course my other bike is a supermoto and I am a hooligan at heart.