A question close to my heart.
The AU intech SOHC is a bit more torquey feeling low down, I think the Barra gets to peak torque a little higher? Otherwise both robust. I'd say AU (or early AU2?) for that extra ground clearance the early models got - they were apparently great dirt road tourers back in the day. Live axle rear which got panned in the press is actually a bonus 10 years+ on. Front ball joints seem to be the thing I most did and redid in my old Falcons...
As for the Commodores
OP lists, Ecotec is reliable & in all of them except the VZ which got this alloy thing that ate timing chains - beware! Touch not the alloytec! As for the ecotec, it can short out an electrical lead connection on the alternator, there's an aftermarket part that is more sensibly designed. Can leak at rocker covers. Dad's VY does go through power steering fluid pretty quick. And early ones (VR-VS) would forget to send timing information from sender unit near harmonic balancer on hot days and shut down all power while on the move. Intermittently. Fun. Commodore wagon also has
IRS which tended to eat inside rear tyres until VX2. They are pretty cavernous inside, being designed to Telstra's brief! I'd reckon they are a bigger/taller load area than the Falcon wagons of same era - does anyone have any dimensions to compare?
Overall, AU is the winner but it's getting old now, so latest BF you can find at a nice price?