My previous car was a CLK 55 AMG (2000). I changed for a Coupé CC in 2002. Still driving and loving my daily-driver car, around 114'000 km today. The MB was an excellent car but the Mas' better fit my needs because it mix a luxury and a sporty car. The MB was first of all a luxury car, with a lot of power. Handling was not very good, a manual gear-box was missing (but the auto gearbox of MB are the best auto gearboxes), the car is too much "disconnected" from the road and weight distribution was not at my taste, too much on the front; the MB was difficult to drive on wet roads or on snow. The two different modes (suspensions/gearboxes/ESP) is a real Pro for the Mas'. Maybe a Pro for the MB : the trunk is very spacious. A Con (in my opinion) against the MB is 99% people cannot tell the difference between a CLK 200K and a CLK 55 AMG ! I don't want to pay more than twice as much as my neighbor for the "same" car !
Go for the Maserati, it is a very exclusive car, a luxury Coupé that can transport 4 people, a sporty italian car you can even track. But if you want to be more discret and do not like to too much "activate" your senses, go for the MB. It is very difficult to consider the Mas' as a simple car, it is more like a drug...