[deleted] Well they're both the same. They are both sub-domains. "www" is just a sub-domain too.
Honestly though, this topic is fairly nonsensical and just turning into a religious debate on one or the other. Either way, search engine optimization is more than likely going to be a much discussed topic in the future. It's safe to assume extension development is going to be a key component to this, so let's all just wait until then before we jump to conclusions.