This was my mind with the take on things to some degree too. We have alot of ice/snow measured in the meters so q4 is a no brainer really as well as when I took them for a test drive (also, my previous Bella was q4 too) because really wanted to confirm the differences, my Alfa dealer let me drive one of his friends cars with the Autodelta Q2 gizmo as well as the normal Brera Q2 without the Autodelta doohicky back to back followed by the Q4 3.2 along the same route, which was extremely windy with a few really good straights. i came away as I did the first time round choosing the Q4 version even with its minor drawbacks.
I agree whole heartedly with vegard_dino about it lacking power (it really deserves a twin turbo or a supercharger to really bump it up to even anything close to what would be considered a semi-sports car), due to the vampyric losses from the Auto-box as well as the Q4 system. Yet even in saying that, it is not a high end sports car with gobs of lightened parts or even close to top-of-the-shelf suspension accumen...its just simply a really really great GT and needs a really comfy spiffy jolly good 'ol rodgering in the hills. Q2 is more of a symptom of weight and the heavy [POS-Ausy 6pot] hanging just too far over the front axle that effects the soft stock suspension in hard corners. That as well as offering the mill and drive train options options because ALfa has always been FWD with the few classics that were RWD...alas, those days are done! But FWD is just an option to pull around the rear dead weight of the whole back end ha ha ha.
But ask yourself, are you buying it for track day weekend worrior sessions or as a functional DDriver with more than enough capacity to fullfill your needs with some nice spirited driving thrown in the mix.
Another positive is that ALfa in all of its vaunted wisdom has even let you have enough room to grow with your choice of Bella by leavinig out many sure footed and needed performance specs so that you can create a new hobby for yourself gated around your car, this way you have an excuse to covet the garrage to hide from the missus.
When I was looking for my Berea, I also had the same things going around in my mind. Q2,Q4????
But, I did go for the Q4. Why?
Did a test rive on some mountain roads with ice. Great feeling with the Q4.
Yes, the 3.2 is lacking some power. But, the Brera is a GT, not a sports car. So, I find it ok.