foo.com/* -> www.foo.com/* seems "cleaner" to me than your opposite, due to the issues with cookie leaking, CDN hosting, "normal user" expectations, etc. Like, please appreciate that your usage of "cleaner" is at best subjective ;P. (And I don't quite understand how you are intending to do "foo.com/ -> foo.com"... all URLs must have a path: you can't just GET, you have to GET /.)