Moving it in a sub folder in your main site will be more beneficial . Speaking from experience we've seen the sites we've worked with gain a relevant amount of long tail traffic when we implemented this strategy.

Subdomains DO NOT always inherit all of the positive metrics and ranking ability of other subdomains on a given root domain. If a major motivation of the blog is to pass juice then definitely build it in a sub folder.

I forget the link to the study but Post-Panda some webmasters actually resorted to moving content to subdomains as a work around to their content woes providing further proof that sub domains provide a buffer from negative or positive metrics of the root domain.

In summation I really feel it is the intent of the blog that you should consider when making this determination but in your situation I would suggest following your current direction , More info here for further reading .

Hope this helps ... Cheers Mate