What are the differences between the iPod nano 4th Gen models? What are the differences between these models and the iPod nano 3rd Gen models they replaced?

Please note that all iPod models mentioned in this Q&A have been discontinued. The iPod nano 4th Gen was replaced by the iPod nano 5th Gen on September 9, 2009.

The Apple iPod nano 4th Gen -- perhaps acknowledging the relative underacceptance of the "fat" iPod nano 3rd Gen that it replaced -- is more reminiscent of the "skinny" iPod nano 2nd Gen, but features a slightly thinner (0.02 inch) new wraparound "curved aluminum and glass" case offered in nine colors -- silver, black, purple, blue, green, yellow, orange, pink, and (PRODUCT) RED Special Edition -- as well as a portrait-oriented 2-inch (diagonal) color LCD display with a blue-white LED backlight (320x240, 204 ppi).

Photo Credit: Apple, Inc.

The iPod nano 4th Gen uses either 8 GB or 16 GB of flash memory, capable of supporting 2000 or 4000 songs, 7000 or 14,000 photos, and 8 hours or 16 hours of video, respectively. Unlike previous iPod nano models, all colors are available for both capacities.

Compared to the iPod nano 3rd Gen models, the iPod nano 4th Gen also gains a variety of enhancements including a built-in accelerometer that automatically switches to "Cover Flow" navigation when the device is rotated into "landscape" orientation (games and videos only play in landscape), a new "Genius" feature to dynamically create playlists based on "songs that go great together", and shaking the device gently now "shuffles" songs. Battery life for music is an unchanged 24 hours, but battery life for video playback drops to 4 hours from the 5 hours provided by its predecessor.

The interface has been "enhanced" but continues to use "MacOS X Leopard" inspired interface elements derived from the version of OS X unveiled with the iPhone, but adds new accessibility options including larger text and spoken menu items. Other worthwhile but more modest improvements include integrated support for Nike + iPod, support for FM radio "tagging" using the previously released Apple Radio Remote, smooth audio "crossfade" as an option between songs, and the iQuiz music and movie trivia game has been replaced with Maze (Klondike and Vortex still are provided).

Differences between iPod nano 4th Gen models are extremely modest -- and since all colors are available for both capacities -- can be summarized simply by capacity and price. For your convenience, the variations are summarized in this handy chart:

Differences between the iPod nano 4th Gen and iPod nano 3rd Gen models are more substantial:

† The 4 GB configuration of the iPod nano 3rd Gen only was available in silver.

* Although Apple did not officially announce such a model, third-parties have reported that a small number of 4 GB configurations also were released to some countries priced at 119 Euros. Perhaps Apple originally had planned to offer 4 GB models but decided against it after some units had been produced and shipped.

** By default, the iPod nano 4th Gen is oriented in portrait mode (240x320), but due to an accelerometer, automatically switches to landscape mode (320x240) when rotated.