I've been playing with uploading videos today and MSN Video seems to outshine the other when it comes to uploading as well as viewing video.
The biggest strength being the uploader that comes built in to Windows Live Photo Gallery. With YouTube you need to wait for the whole video to upload which can take quite a lot of time, if not you need to muck around with some compression program and fine-tune the settings before doing the upload. I don't have the patience for that.
The Photo Gallery uploader seems to compress the file as it uploads making it extremely fast.
Then Windows Live Writer makes it as easy as Insert->Video to allow you to pick the video that you uploaded.