There are differences in pronunciation and some minor differences in spelling. Slang is different, too, but each is understood by a speaker of the other. Which is better? Personally, I don't think it really matters much. The differences are minor anyways. I suppose it would all come down to a matter of preference or where you wanted to live or visit.

Better for what? =P The only difference is the accent and a few words here and there. But I'd vote for Australian English. It sounds funny and I always think of Steve Irwin when I hear it.