Subdomains vs Subfolders

[Optimise]

I've had a good read on this one and just wondered whether the info on the below link is still valid 3 years on:

http://www.seomoz.org/blog/understanding-root-domains-subdomains-vs-subfolders-microsites

My main site is a forum but I want to add further content in the form of a blog.  It seems logical to me that domain.com/blog/ would make more sense than blog.domain.com as the the content and inbound links to the blog would also help the forum where it's on the same subdomain, however I just wanted to make sure that was still the case as I've also read that Google now see a subdomain and subfolder in the same way if set up correctly in webmaster tools and this solution would look neater if that was the case.

Thanks all.

[Jellyfish-Agency]

Rand,

Do you still stick by this, or have you noticed a shift in the metrics given the update from Matt Cutts on this very subject.

Should I structure my site using subdomains or subdirectories? http://www.youtube.com/watch?v=_MswMYk05tk

[randfish]

I just mean the uniquely named portion of the subdomain, e.g. the "xyz" in xyz.domainname.com

[Optimise]

Thanks for clearing that up Rand, I'll stick to the one subdomain.

[SEODinosaur]

What is subdomian extension? I cant find it in Wiki or Google. When would one use it?

[randfish]

All the testing, research and examples I've seen in the past few years (and even the past few months) strongly suggest that the same principles still hold true.

Subdomains SOMETIMES inherit and pass link/trust/quality/ranking metrics between one another

Subfolders ALWAYS inherit and pass link/trust/quality/ranking metrics across the same subdomain

Thus, having a single subdomain (even just domainname.tld with no subdomain extension) with all of your content is absolutely ideal from an SEO perspective. It's also more usable and brandable, too IMO.

[Optimise]

These links are the one's that got me thinking.

http://www.mattcutts.com/blog/subdomains-and-subdirectories/

http://www.webmasterworld.com/google/4339166.htm

Also, I was under the impression that sub forums on one domain were viewed as different sites in the SERPs but try searching for 'bodybuilding'.  You'll see www.bodybuilding.com at the top and a list of pages from that site and 2 further subdirectories are included (forum.bodybuilding.com and bodyspace.bodybuilding.com).

Although a personal preference only, I prefer subdomains and think forum.domain.com and blog.domain.com look much better than domain.com/forum and I would do it this way IF the rankings were unaffected.

[Steven_Macdonald]

I've read tens, possibly hundreds of articles on subdomains vs folders.

I still prefer the folder approach (it makes more sense to me) but I'd be interested in seeing the article you refer to that says Google now views SD the same as folders. Much appreciated!