...with Netflix you pay a monthly fee to stream movies and have new releases sent to your house on either DVD or Blu-Ray. With iTunes or
Amazon Video on Demand you are renting each movie you stream. You are paying per movie, not a monthly fee. It would be the same as going to the Video Rental store and getting the new releases except you don't have to leave your house.
Netflix is the best deal going in terms of value, now that they offer streaming content (I'd never use the dvd service). My chief reason for preferring
Amazon's Video on Demand over iTunes is that if you buy a digital copy of the movie or tv show, you can stream it forever, from anywhere, but even the cheapest rentals and purchases can't beat $9 a month unlimited. The downside is the content is older.
My 2nd pick is still
Amazon, because you can stream your rentals and purchases from anywhere on any pc - you just log in to your account. With iTunes, you have to download it and use up your drive space - a critical issue, with the iPad's limited resources. Also, movies from
Amazon are
much cheaper - they regularly have $5 specials on movies and $10-$15 tv seasons. I've seen some shows for $40 on iTunes that I bought for $14 on
Amazon.
The sole benefit of iTunes is their sweetheart deal with the Disney group of companies, as content from them - like tv shows currently on ABC - isn't available elsewhere. On the music side, they seem no cheaper than Rhapsody. The iTunes app does keep playing in the background, which Rhapsody's doesn't do (yet).