I've ridden both of those bikes. I'd say the Piaggio is only a good BOV if you're 100% sure you're going to be on clear paved roads the entire time...remember that the twin front wheels aren't driven...which means they're going to drag in mud like a mofo.

The 1200GS is a great machine if you have the money...but...it's very tall and very heavy (I'm not 100% sure but I think you can get a 36L tank for it! you could for the 1150GS)...also very hard to manage in true off road conditions. Watch the Long Way 'Round with Ewan McGreggor and you'll see just how much they fight with the bikes. I think Charlie separates some chest muscles later in the trip pulling the bike out of muck for the millionth time. I used to work in a BMW motorcycle dealership and being the closest dealership to Alaska, I heard a lot of stories from guys making the round trip from the US...some of them were pretty bad. The guys on the 650GSs always fared better as the bike is way more manageable.

In that same TV series the camera mans bike breaks down so they replace it with a cheap Russian machine and he is super happy because it never breaks down and deals with the local terrain WAY better than the BMWs do...if I recall at one point he laughs at them as he rides past their stuck bikes.