Yes I think my self I root is better and eayer to rank that a subdomain, but subs can be ranked as well I have seen lots of websites with rankings on subdoamins.
Remember that if you are using a subdomain you should use it at the start of a new section, and yo0u should not aim more that one subdomain at that section. Also make sure you dont have a root path aiming at that section as well these will be classed a duplicate content by the search engines and will not help in any rankings what so ever
