Tracks and racing styles differ greatly Greg and will certainly "improve" many horses times, the Kiwis have a number of big tracks with slow surfaces like grass for instance.
I certainly wouldn't think Aussie trainers are across the board superior to Kiwis,if anything it would be the other way around, but not to any great degree either.
Some horses will not go so well here for any number of reasons, not the least previous trainer had the "key" to the horse, whether thats in his shoeing, work regime, gear etc etc.
The usual stuff with horses Greg, more questions than answers!!!
Cheers,
Dan