I know this post is a bit old, but for anyone who stumbles upon it I think that it should be noted that in late 2011 Google converted all of their YouTube dofollow profile links to nofollow.
Therefore, I think that the argument of back link building because of the follow is irrelevant between the two services. From an SEO standpoint more merit should be given to the fact the YouTube is the #2 ranked search engine which could generate site traffic if your content doesn't get washed away by the 70 hours of video being uploaded every minute. For integration purposes and customer satisfaction I prefer Vimeo as it doesn't have all the adds.
The best, and obvious answer, should be to self host them and use an HTML5 player if you can. Here's some good reading for more on these services:
