It's hard to keep count of how much content lives on various video stores, but Amazon's Instant Video store has all the major studios and networks just like Apple does. Now that Amazon Instant is on the world's most popular tablet, is it a more effective rival to iTunes? There are a number of differences and advantages to each service, but Amazon has definitely closed the gap more than ever before. That's in addition to its presence on Xbox 360, PlayStation 3, Roku, and many other home video and TV products. Now, however, Amazon Instant Video is available on the iPad. But until recently, its lack of availability on most mobile platforms has been a drawback. Splitting the difference was Amazon's Instant Video: it offers a diverse library of pay-per-view TV shows and movies, plus a subset of 'free' content for subscribers to the company's $79 per year Amazon Prime service.

For a la carte, pay-as-you-go services, Apple's iTunes has been the default choice for many when it comes to buying, renting, and viewing videos. Netflix is the top dog thanks to its $8 subscription streaming service, but your viewing choices are severely limited. The future of TV, movies, and home entertainment feels like it's changing by the day, thanks to the impact of the digital revolution.

How to watch movies on itunes