I personally think it's the best way to go for most videos.
-It's the 2nd largest search engine on the web, so you'll increase audience.
-It's compatible with most portable devices, including iPad, so more people can watch it.
-If you upload a quality file, it looks pretty darn good.
-Their insights are awesome, so you can learn who is watching, how they are watching, how they found it, and more.
Vimeo is higher quality, and most of their videos are compatible with iOS devices, but I still opt for YouTube.