Google has some pretty cool stuff on there but the compression drives me nuts. It's like watching through a magnifying glass or something. Hell, you can barely even read text on most google vids. Some of the vids on YouTube are just as bad but overall, I think the image quality is a bit better.
Youtube has a bunch of MyspaceWhore-type people constantly coming over brand new videos as soon as they're released, constantly looking for any new videos that interest them, etc. Plus the servers (believe it or not) have had a better uptime than the Google Video.