NDS:Nintendo DS Model Differences
Page content & researching collaboratively taken from io55.net's Nintendo DS page with permission.
There are four Nintendo DS models.
Models are arranged chronologically.
Nintendo DS (2004-2006)
The “Classic” Nintendo DS, easily identified by it's “bulky” design with ridges on the outer shell, rectangular start/select/power buttons, and speakers with many dots. Being Nintendo's first crack at the DS, and the only DS model to release somewhat in the 6th generation (complete with GBA slot), this model has a few small weaknesses compared to it's followup, the Lite. However, these weaknesses are minor - a shorter stylus, slightly lower battery life, and slightly darker screens. Otherwise, the original DS is a perfectly serviceable system that can hold it's place as a worthwhile device.
Nintendo DS Lite (2006-2011?)
Despite being the 2nd version of the DS, the Lite is what most will think of when they recall the “Nintendo DS”. Wildly popular in sales figures, the DS Lite is a very common system. Improved on the original DS by making the case sleeker, lengthening the stylus, increasing battery life, and making the screens brighter and more vibrant. Easily identified by it's circular start and select buttons, presence of a GBA slot, it's sleeker “perfectly rectangular” design without shell ridges (only a logo), speakers with less holes, and a power slider on the system's side. It is also important to note that the DS Lite has an understated feature - a pressure-sensitive touch screen. It's unclear if all DS Lites have it or not, but even if a DS Lite does have pressure sensitive screens, only a few pieces of software actually use it (mostly homebrew), making it a simple curiosity at best.
Nintendo DSi (2008-2012?)
A major update to the DS line. Easily identified by it's triple power/charge/internet LEDs, a camera, an SD card slot, and a size closer to the DS Lite. Changes arriving with the DSi were significant, as the DSi introduces an entire operating system to the DS, downloadable software unique to the DSi line, a camera and microphone, the possibility to softmod and emulate systems directly on the device, a faster CPU and more RAM, internal storage + SD card slot, and generally superior screens. However, the DSi does have one good feature removed - the GBA slot. Essentially, the DSi is what pushed the Nintendo DS line into “matching” Nintendo's then-flagship console, the Wii, in “non-gaming” capability.
Nintendo DSi XL (2008-2012?)
Very similar to the DSi, for obvious reasons. At first glance, the DSi XL appears to simply be a larger version of the DSi. However, certain improvements over the original DSi make the XL a better system in several aspects. Most importantly, both of the screens on any DSi XL are guaranteed to be IPS screens, or in other words, guaranteed to have superior viewing angles, superior color reproduction, and superior brightness. Furthermore, the XL has slightly better hinges (can lock at a 120 degree angle), generally longer battery life (a few more hours over the DSi), and louder speakers with better enclosures.