The best deepwaters tend to come from Indo along with some sick SPS, and the best maricultured colonies come from Bali.
Fiji has the best consistency in acros overall, and a ton of the "Aussie" acros are actually Fiji labels that the wholesaler/retailer threw the Aussie name on for markup. Chances are if you've got a nice acro in your tank then it came from Fiji.
The Solomon Islands is where the purple Acropora tortuosas come from, as well as the pink lemonades and purple monsters. I'd say the hardiest ones are from the Solomons and Indonesia.
There's very few acros in the hobby that actually come from Australia, just the blue echinatas and shortcakes and a few others here and there. There's at least one wholesaler and quite a few retailers who fudge the origin on their acros as "Aussie" for a quick buck.
Tonga doesn't have too much in the way of great Acros, at least not that I've seen.
I'd say the best overall would be a toss-up between Fiji and Indonesia, I've seen some of the nicest pieces come from both places. I prefer Indo because I like deepwaters and they get some ridiculous ones from out there.