Very thoughtful review. Very nice to point out what you thought was plus and minus. I did exactly the opposite and sold my 2010 GTR to purchase an 2011 M3, mineral white with competition package and full Dinan upgrades.
I completely agree about the BMW engine "lacks of" compared to vehicles in it price range. The reason I switched. My GTR was falling apart. If you put it on the track and race it as hard as an M3. I guarantee you will be in the shop tightening and replacing almost every part in less than one year. Just driving hard on the road, no problem. But put it in a Nasa TT races with 4 seasons a day for a weekend and once or twice a month at different tracks. You will find, it is not the car you thought. My M3 takes the abuse day after day and says, "is that all you got". Of course brakes and tires need replacement. The GTR is faster, agreed. But after 3 transmissions, 3 turbos, dash cluster, rear end complete replacement, awd gear box, Oil pump, and two power steering pumps, fighting everytime with the Nissan dealer for a warranty at only 14k miles. I gave up. It was like a Jaguar, in the shop more than in my garage or at the track. I really wish you the best and hope you never have a problem. I heard Nissan fixed those problems for 2013. But then again, they said the same from 09 to 2010. When I bought mine. I just don't want to spend 90k to find out again.
(BTW) I drive a 2010 Maxima as my daily driver, my 2011 M3 is just for the track.