The whole Diesel vs Petrol debate is one that is really boils down to personal taste & driving style.
For me, I'd never have a diesel Alfa. It's not that I don't like diesels, they have their place; my VW is a diesel & gets used for long distance visits to customers & taking crap to the tip on Sundays.
The Alfa, on the other hand, is for when I want to have fun & for me that rules out having a deisel one.
Petrol & a V6 petrol at that. Get the 3.2, sod the fuel thirst & have a grin from ear to ear!
PS. 156 GTA is even better. Glorious sound from that Busso V6!