The factor that's missing for me is how hospitable countries are to strangers from other cultures and often other religions. Americans aren't as universally loved as we'd like to think. Another factor is convenience. So many people complain about life in the US, not realizing how darn convenient it is (assuming of course that you have at least moderate means). Having said all that, if I could learn Portuguese, I'd likely seriously consider Algarve for at least part of the year.