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Hi John, Subdomains are technically different websites, I don't see why Google would give your main website the benefits of the SEO gained from the sub-site. With that said, having it on its own URL is preferable  purely from a click-through perspective. Users are much more likely to visit and spend time on a site that's clearly its own over one that seems like a 'bolt on' to someone elses. I hope that helps! Andrew