I usually use YouTube, just because I like the format better and I can check my videos easier. Google Video is good when something isn't on YouTube though.
YouTube: YouTube is probably the more populated site rather than google video, and you can find just about anything on it, yet there are many annoying comments and things in videos that can disrupt performance.
Google Video: Not bad, can search through YouTube videos also, and can be good location wise. For example at the moment I'm in China, which filters YouTube with "The Great Firewall of China", yet i still have access to google video.
[quote=blkasp]Oh and by the way, Google created Youtube.[/quote]
Nope, Google bought YouTube.
Although I think YouTube is better and they have better features, especially since you can't upload videos onto Google Video anymore. However I don't really see the difference because Google still owns YouTube (like, literally like owns them not like "PWN3D!!!1".
The only annoying thing about YouTube is the ads these days, they're getting annoying. I suppose you can just minimize them though, but it's still annoying.
Of course Google gets their videos from Youtube. Youtube is owned by Google. Google Video is a search engine - just like plain Google. It's just better for searching for videos than Youtube is, since it searchs many video sites.