I've always found it interesting that SEOmoz don't have a channel on YouTube so would be curious on their view for this.
At Koozai we host videos on Wistia and then display those on our site. We did use Vimeo but they can ban anything promotional (even for paid accounts) so we didn't like the risk. YouTube was avoided as then people can advertise on your website via AdWords so we didn't want that.
From an SEO point of view the best thing to do is to use YouTube as it's one of the most popular search engines so you'll get potential to be found on Google and by YouTube searchers.
