Australia - Buy imported or local version?

It should not have any effect on your access to any server. Right now, the server selection screen is like a browser window - you can view every US and EU server just by clicking on the appropriate tab - tab 1 for US, tab 2 for EU. The recent Q&A clarified that Oceanic servers will simply have their own tab (presumably tab 3). So you would still be able to play on a US or EU server should you desire to do so (and US and EU players can choose to play on Oceanic servers, as well).

In effect, there are no 'local versions', in the sense that what you can buy on March 1 is basically the same copy that you can buy now. So you can just focus your buying decision on total cost and shipping time.