BA has more tech in it i.e. the
ICC etc - all good in theory but costs more to fix should something go wrong.
Both AU and BA have their own faults which are fairly well documented by now. Forget any Falcon for resale value least of all the BA's - look at the prices you're seeing now and think about what those cars would be worth in 4 years time - thats what you can expect to get too irrespective of AU or BA.
If I was looking at B series cars I think I would skip BA and go to BF - again more tech, but more refined, better inclusions and still very cheap for what you get. BF's just seem to be a better built car IMHO.