domain or subdomain

Greetings

My 5 year old domain enjoys over 40,000 entries in google.
I currently run a successful forum, and I'm about to start a couple of new forums. My current forum's URL is in a subdomain form:
forums.domain.com

My question is: is it any better if I start each new forum with its own domain name? or should I better just run each as another subdomain to the same 5 years old domain name that I started with?
Thats of course in terms of popularity and search engines indexing and ranking etc..

what is the pros and cons of a new domain in comparison to a subdomain of an already heavily indexed domain?

Thanks for your thoughts and sugestions in advance

Think about what your users would like. A simple domain is easier then a subdomain for every forum.

Its own domain name would be better. A new subdomain on a site is treated exactly the same as a brand new domain name by the search engines, so you will be starting from scratch either way. Putting the new forums in a directory of the old domain, like domain.com/forum would be the best bet for getting the new forums rankings up quickly because all of the new pages would still be part of the old domain and would already be out of the sandbox, and also help give your site the "amazon effect".