As with the Nintendo DSi XL, the 3DS XL features larger screens and longer battery life than the original 3DS. The screens are 90% larger (top: 4.88 in (124 mm), bottom: 4.18 in (106 mm), and the battery life is increased by 86%, while the weight of the console increases by 46% (336 grams). A 4 GB SD card comes packaged with the console instead of a 2 GB card included with the original 3DS. The 3DS XL does not work with the original Circle Pad Pro, but a compatible version of the accessory was announced as a future release.
Source: Wikipedia, "Nintendo 3DS", available under the CC-BY-SA License.