1150 or 1200 or 800gs?

My friend wants to buy a second hand BM. His weight is roughly 135kg and he is quite tall. He asked me weather I would buy a 1150gs or 1200gs or 800 gs when one ceep service cost reliability ext in mind. I am not a "big" BMW bike expert so basically I told him I would buy any of them depending on price. Are there any comments out there on witch one to buy - his budget is roughly 70 - 80 grand. This would be his 1st big bike and he really want's a good quallity ride.  Please, he is only interested in BMW, so don't try and convince him other wise