In Axis and Allies, should the UK Build a factory in Australia?
I would also echo the India first, mainly to fortify Asia from Japanese expansion on the mainland (what else is there, some infantry in China?). Australia is isolated and would need to build vulnerable transports to move anything to island hop.

In games that I've played, the second factory has depended on what the enemy has done in the first two turns or so. If Germany makes a hard push for Africa, I look more to build in India. If Japan makes a hard push in Asia and is successful in taking China, South Africa is more my choice. And if by sheer (bad) luck Germany takes over most of northern Africa and Japan is powering through Eastern Asia, then I look at Australia and try to get the US player to help put pressure on Japan's Eastern flank.