Sub-domain Vs. Sub-directory in the eye of Google Bot
Hi! I find this nice topic and take the opportunity to share it with you all. It relates to a prolonged debate on Sub-domain vs. Sub-directory and how GoogleBot sees them. Just a nutshell of the long post:
GoogleBot prefers subdirectories, i.e., www.domain-name.com/dir more than sub-domain www.sub-domain-name.domain-name.com, as it the bot was designed to crawl sub-directories. However, the biggest advantage of having a sub-domain was that the Bot would treat each sub-domain as independent website. Therefore, possibility was there to see more than one search result for a specific query from the same website containing a number of sub-domain. SEOs used to take advantage of this by going on increasing number of sub-domains.
Recent changes in algorithm seems to have fixed that. I’m not going to tell anything more but to suggest you to follow this link.