Sub Domains or Multiple Domains? Which is a better way to go for blogs?

[amitjain]

We just can’t decide what the answer is, particularly from an SEO perspective.

We want to run multiple blogs on different categories, please assist on deciding should we go with different blog domains or create subdomains for each category.

[RyanKent]

I agree with everything John shared but wish to clarify one point:

We want to run multiple blogs on different categories

If the categories are different but related, then I prefer John's approach. If you have a site that talks about "cars" and you want to offer a "Ford" directory, a "Toyota" directory, and so forth then I prefer the approach John shared.

On the other hand, if the categories are completely unrelated, then I would recommend using the subdomain approach so each domain can keep their focus.

If one blog talked about cars, the second was about diabetes, the third was about poker, then these blogs clearly lack a uniting theme. To help each domain remain relevant for their primary topic, I would suggest using different sub domains.

[john4math]

Usually the best thing to do is use subdirectories on one domain, to consolidate your domain authority/strength.  Here's some reading if you want to learn more:

• A recent Q&A about it with a staff endorsed answer: http://www.seomoz.org/q/subdomains-vs-subfolders-for-unique-categories-topics
• An SEOMoz blog post about it from 2009: http://www.seomoz.org/blog/understanding-root-domains-subdomains-vs-subfolders-microsites
• A presentation mostly pertaining to these choices for international sub-sites, but still relevant: http://www.distilled.net/blog/seo/mozcon-international-seo/