Msg#: 4392910 posted 4:16 am on Dec 3, 2011 (gmt 0)
If you choose a 301 the link juice will be transferred from folder to sub domain. Please note 100% link juice will not be transferred and you will loose some of it (As per Mr. Matt Cutts). You need to develop more links for your subdomain to maintain your previous position.
Msg#: 4392910 posted 2:18 am on Dec 6, 2011 (gmt 0)
although this doesn't answer your precise question, it implies that there is little difference between subdomains and subdirectories since subdomains are now categorized and reported as internal links in GWT.
Msg#: 4392910 posted 10:28 am on Dec 21, 2011 (gmt 0)
"They are considered the same as a directory under main site" - NOPE!
subdomains do not pass value to the main domain the way subfolders do... since Panda update it is suggested to put all your low quality content on a subdomain - this will improve the overall health of a domain.
and the root domain is not passing 100% of its value to a subdomain... as opposed to subfolder.. so if you want better rankings under a trusted domain - go for subfolder!