WordPress.com uses WordPress.org. (What?!) When you see references of WordPress on this website, it’s more than likely referring to WordPress.org. WordPress.org is a stand-alone Content Management System, or CMS, that is generally hosted with a different server (such as GoDaddy, Blue Host, 1&1, Flywheel, or Host Gator to name a few). Plus, WordPress.org is a little more flexible when it comes to making cosmetic, drastic changes to your site. But, it can have some security issues if not hosted properly.
WordPress.com is a managed WordPress blogging platform and social community. It’s mainly for people who love to blog (online journal). While you can make some changes to the theme (and even add plugins, but you’d have to pay extra), it’s more challenging for web designers to make cosmetic, drastic changes. However, WordPress.com is managed WordPress, so it is very safe and secure.
While Unity Tenth would rather work with WordPress.org, at the end of the day, it is your organization’s decision as to what works best. Greg Narayan has a YouTube video that has a very recent explanation of the two platforms. You can watch the video below to get a better idea.