Pages that have a page name set can also be reached under www.facebook.com/name
– so that’s no realistic way of distinguishing a user profile from a page.
Your only option would be to make an API call and look for fields that are only available on pages, but not user profiles (or the other way around) – pages have f.e. category
or is_published
, whereas only a user profile would have f.e. a first_name
.