[apexalpha]

the reasoning is the following:

>Note on subdomains: every subdomain, to Google, is a different website. So if your domain is flaviocopes.com, and you create your blog in blog.flaviocopes.com, then that’s a completely new website to Google, and it will have its own ranking separate from the main domain.

So from a SEO perspective it might make sense, if you're running a small blog and traffic is one of your main goals.