De acordo com o Google, é melhor usar o 301 Redirect. Trecho da resposta da Central do webmaster do Google :
People access your site through several different URLs. If, for example, your home page can be reached in multiple ways - for instance, http://example.com/home, http://home.example.com, or http://www.example.com - it's a good idea to pick one of those URLs as your preferred (canonical) destination, and use 301 redirects to send traffic from the other URLs to your preferred URL. You can also use Webmaster Tools to set your preferred domain