Vimeo is slow, offers poor quality, has a childish UI, has limited content and is poorly supported.
YouTube on the other hand is fast, offers decent quality, has a smooth and modern UI, has tons of stuff and can be used on pretty much any device you can imagine these days.
YouTube is the clear winner.
"Limited content" utter rubbish. a lot of excellent videos are found only on vimeo you just need to look harder



