subdomain vs subdir?

I'm about to purchase vbseo... and my forum is still young by my site is a bit older... pr3 8 months old... so quick question is it better for me to use a sub dir so that my site would www.site.com/forum or forum.site.com... from a seo standpoint what would be better?

I will have to say sub-directory (www.site.com/forum/) would be much, much better than using a sub-domain but hey, that's just me.

I prefer a subdomain for the board, I got better pagerank since I changed from /forum to forum.domain, both are 5 now and I use to have 4 for domain and 3 for domain/forum, my guess is that the sub directory is at a lower level and that means it is less important, so the pr flow is lower. This makes perfect sence if you look at most sites the sub dirs have lower pr. Also it looks mutch better.

Pagerank is not effected in anyway by document location. PR deals with link cycles, and more over, is pretty meaningless.

I've said this 1000's of times now, but IMO, unless you need to point a domain, or in this case, part of a domain, to a different server, use a normal subdirectory. subdomains are just that-- SUB domains, a seperate part of your site.

example, groups.google.com, or mail.google.com vs google.com. Their email and listserv have nothing to do with their main site, a search engine. Thus, a subdomain makes sense.

but if your sites' forums are an integral part of your main .com's theme, and it resides on the same server, i see 0 use in using a subdomain.

keep in mind also, subdomains are tracked as seperate entities, similar to how domain.com/~username are.

If you look at directories for example you will always notice that pr flows from the homepage to lower directories in a way that it is reduced.

www.yourdomain.com pr 10
www.yourdomain.com/forum will have pr 9
www.yourdomain.com/forum/f10 will have pr 8
and so on.

This is only logical because a homepage is always more important than other pages, so naturally gets more links to it and pr that is passed on in or off the site needs to be lower than it's source according to the algorithms.

www.yourdomain.com pr 10
is linked to
forum.yourdomain.com
and vice versa
So the forum is equally important to pagerank because
1. there is no subdirectory (meaning the document is at /home/
2. it's a subdomain linked from and too the pr source <-->

I hear people say this is not true because it doesn't matter where the document is, YES that's right if you are talking about pagerank flow from other sites to yours. But when you are talking about internal flow, subdirectories are less important than it's source, unless it's not a subdirectory. You do not have to believe this, I've experienced it myself. I use to have the old domain/forum and it was always lower than the source it was linked from, since the latest PR export the subdomain has identical pr, even with less links to it (only from the main domain).

Internal structure is VERY important and IMO domains always win here. Now you need to carefull not to abuse this system because Google knows this weak spot all too well and if you think you can set up 100 subdomains just for showing your forum categories for example this can result in punishment.

So yes only use them for very important parts of your site that have totally other technical uses. A homepage contains articles, a forum contains posts and let users add content, so these are clearly two different things that can be seperated.