It depends on what you mean by "better." I have never once watched a Netflix stream without the movie's video freezing while the audio continues on. Usually happens at least twice, and "threatens" multiple times during a movie by the video jagging for a bit.

Amazon's pay per view streaming rental has consistently been all but perfect play.

So Netflix is better on price. Amazon is better on getting absorbed in the movie and not being thrown back into your living room because the movie stopped.

Youtube/Google's streaming rental quality is good, even great, except three out of the four movies I tried suddenly stopped and reported elapsed time as that the entire movie had suddenly been watched. Movie had to be started over, virtually ruining the experience. They did refund the rental fee without question.