The reasons that I bought an A2 and not an A3?
First, cost. Usually an A3 is newer and costs more. If that is not a barrier for you, so be it.
Second, I like the idea of the multi-fuel engine (instead of "only" diesel).
The most important reason for me? The A2 I consider to be EMP proof. The A3, with its CTIS and automatic tranny, has too many electronic circuits on board to survive an EMP attack and be CERTAIN that it will still run. (Call me paranoid, but that's my logic!)