When people think of online video they think of Youtube. YouTube is the number one video-sharing site on the web. If you're a casual video uploader, blogger etc... and uploading convenience or longer videos might be more of a priority, YouTube may be a better choice. I think Youtube is a great service that has allowed film makers an audience that they could never accessed before.
I have noticed many film makers use Vimeo. If you're a creative filmmaker, you might get better feedback and engagement from the community on Vimeo or better access with their premium business account option. Vimeo videos are much cleaner and require much less bandwidth for viewing. They are slowly but surely raising the quality ceiling in its encoding of your media with different frame rates.
The guidelines now properly state support for 23.976/24, 25, and 29.97/30 frames per second. Videos of higher frame rates are recommended to be halved in encoding — for instance, 60p would be encoded at 30 frames per second. This is some good stuff for film makers to show their work in the frame rate it was produced in!
Online video is getting better all the time!