They are both great cars, for different reasons.
Before I bought my M6 i drove a bunch of others in its price range, some higher and some lower. The GTR was one of them. AWD is nice, It is fast but for me, the combination of power, handling, drivaebility, comfort and luxury were what I liked in the M6. And ya, I cant get over the fact that its a nissan. My first car was a nissan sentra
My M6 will never see the track