According to the mechanics at the dealer, the 2.4 JTDm is the best choice for the Brera, the smaller ones being underpowered for it and the 3.2 being relatively underpowered, thirsty and on a car that is heavier because of the 4WD. I'm personally very happy with mine (when it works!), it's a beautiful looking car, it's very comfortable and it's classy.
I am also thinking long term, and wondering what it will be worth in a few years, but there have been cars looking way worse than it which made it to the collectors' market and fetch very good prices.. I dunno if I'm gonna sell it or keep it at some point, but whatever the choice, I will always be very fond of it and will think of all the good times I had with it..
Alfa is just a legend, period.