I would argue that the differences between these two are much more common than the similarities. Although some have called Australia's treatment of aborigines genocidal, it is something of a stretch to equate it with the Holocaust.
The major similarity is that the white Australians were trying to destroy the society of the Aborigines. In some places, like in Tasmania, this ended up resulting in the actual destruction of entire populations. In other places and times, it was more of a cultural destruction, with forced attempts to assimilate the aborigines. The worst of these attempts was the program of taking children from their parents to be raised in white families and thereby assimilated.
While these are horrible things, they pale in comparison to what the Nazis did. The Australians did not as a rule try to actually kill the entire population of aborigines. They did kill them at times and they tried to destroy their society, but this is very different than the kind of mass killing that occurred in the Holocaust.