With the update to iTunes 10 and the new Apple TV just around the corner offering TV & Movie rentals, I thought I’d try and get a handle on just what the differences are between the old rental model and the new.

As current iTunes and Apple TV movie watchers are aware, movie rentals are already available. Any movie rented through iTunes can be transferred to an iPhone, iPod Touch, iPad, or Apple TV. Apple TV, iPhone 4, iPad, iPod touch (4th generation) have never had the option to transfer rentals back to iTunes.

With the new TV rentals and the new Apple TV the rules change a bit. If you download a rented TV show on your computer, you can play it on your iPhone, or iPod touch if it’s a standard-definition episode (TV episodes in HD can be played on your iPhone 4 or iPod touch (4th generation)). iOS 4.1 or later is required. Once you move the episode from your computer to a device, the episode will disappear from your computer’s iTunes library.

If you download a rented TV show on your iPhone 4, or iPod touch (4th generation) it is not transferable to any other device or computer. This remains the same as the current movie rental model.

All though this information comes from the latest TV episode rental FAQ Support page, the requirements make no mention of viewing rentals on the iPad. This may be a feature to come in iOS 4.2 for the iPad.

With the new Apple TV it’s much more simple, everything streams, either from Apple’s servers or a local machine using AirPlay. This also means that anything rented on the Apple TV will not transfer back to any other device.

So what is the moral of this story. For maximum playability on all computes and iDevices, rent or purchase video content, when you can, through iTunes or your iDevice. You can always stream back to your Apple TV with AirPlay and still retain the ability to play on your local mobile device or computer.