In general, I think it is better to write whatever length is needed to convey your point accurately with adequate explanation. Beyond that, it's a matter of your purpose in writing.
If you are writing for enjoyment and experience and to share your knowledge, then any length is fine. If you are writing for SEO and making money online, then it seems like most people say it should be 700 to 1100 words, or around there.
But quality is King, according to some, and that would dictate that you let the subject matter, not the intent, dictate hub length.
Hope that helps. =D