The 6-erseries is the only BMW, wich I really like, but also I think, the 6er is atm a bit boring. BMW must bring the new generation quickly.
The Maserati is a very nice car, but I personally don't see the italian flair in this car.
So, for wich car I would decide? Really, I don't know. In this comparisation we must have a third Alternative, like R8 or Vantage.