Should I use a subdomain or a folder?

I own a hosting company ( http://hostwq.net ) and I'm looking forward to adding a directory and maybe move my support forums. What I don't know is should I go with a subdomain (forums.hostwq.net) or a folder (hostwq.net/forums)? Would it matter if I choose one over the other? I was going to go with folders but decided I'd post and bounce some ideas around before I make any stupid decision.

Cheers,
Pete.

 

I prefer folders if it's part of the site, but if it's going to have a different design, idea / concept, navigation, etc then a subdomain usually works best.

 

using folder is better for seo.

subdomains are completely new domains for the search engines

 

using a folder is a better option , to much subdomains can even effect your serps.

 

I guess I'll go with sub-domains for my forums and directory since they have different design and navigation. And use folders for other site related stuff. Thank you all who have contributed.