Lol, it is quite the decision, but the fact that you are here must mean that you are heavily considering the McLaren. I think that the exclusivity is a big factor in people's decision to buy something like the 650S. Porsches are nice, BMWs are cool, but not just anybody is able to get a McLaren.
No question... I have to say, after an extended test drive in the 650S, I had trouble sleeping for the next two weeks! This little collage helps me put it in perspective, though. (BTW, I was kidding with the matrimonial reference!)