I'm building a site about many semi-related (but not closely related) sub-topics (for example SEO, HTML coding, and Java coding). Each subsection will basically be its own site (with unique navigation, etc) but sharing the layout and interlinking with the other sections. In this situation, would it be better for me to set up my subtopics as keyword subdomains of the main site, or as subdirectories? AKA, would it be better to have "seo.mysite.com" and "java.mysite.com" or "mysite.com/java" and "mysite.com/seo"? I've heard that Google treats subdomains as separate sites in many ways, but I'm not sure if this would be beneficial in my situation.
Well subdomain is the better way if you are trying to create portal like if you credted one subdomain seo then you can put every topic in this section related to seo.. same as other if you are planning to create only one one page then this is the best way yoursite.com/seo.html and one more thing if you created subdomains then you have to do extra effort on every subdomain.
Each "sub-section" will have plenty of content and pages, the only thing that makes me consider using subdomains is that I hear they will share PR and link power more evenly. Let's say I have five sections, and one gets really popular with tons of incoming links. I know these won't help other subdomains much, but will these incoming links help other subDIRECTORIES with different topics on the same site?