Apple’s iTunes only works on Apple devices, or on PCs running iTunes. That’s no surprise. You’d need an Apple TV, iPad, iPhone, iPod Touch, or Mac to watch what you’ve purchased. On iOS devices, you’ll need to download your purchase or rental before watching — streaming is not an option.

Meanwhile, on Amazon’s new iOS app, free Prime videos can be streamed, and purchases and rentals can be downloaded or streamed. However, you can’t search for content or buy through the app directly: you have to shop on Amazon’s Web site and have the app push your watch lists to you afterward, like the Kindle app. Also, the new Amazon app won’t play nicely with the Apple TV: if you use AirPlay from the iPad app, you’ll get audio only — no video.

Apple TV

Amazon Instant Video works on a more varied set of devices and platforms: PCs and Macs, Roku streaming boxes, the Xbox 360, PlayStation 3, Amazon’s Kindle Fire tablets, and a variety of televisions, Blu-ray players, and other devices from Vizio, Samsung, Sony, Panasonic, Logitech, and LG. It may already be on a Smart TV you bought, and Roku boxes that work with Amazon VOD cost as little as $50. Plus, Amazon’s app is on the Xbox 360 and PlayStation 3, and has been announced for the Nintendo Wii U.

Apple’s iTunes works via Apple TV, but that’s about it. You can access all your previous iTunes purchases (TV shows and movies), and rent new titles at the click of the remote.