Australia Vs. U.S.A. - Economically, Which Of These Two Countries Would Be Best To Live/work/retire Comfortably??

I am from the U.S. And my fiance is from Sydney. He has a degree and I am an admin. Asst. We are trying to research which country would be best to work and retire in, Australia or U.S.A. If you can't answer, can you recommend a website offering free info that will help us decide where to reside and work? Thank you.