The screen is 90 percent bigger, with larger bottom and top screens. It's called the Nintendo 3DS LL in Japan and the Nintendo 3DS XL in the West. The top screen measures at 4.88 inches and is 90 percent bigger, while the bottom screen is 4.18 inches and is also 90 percent bigger.
For the 3DS LL, the battery will last 3.5 to 6.5 hours while playing 3DS games (as compared to 3 to 5 hours with the 3DS). The battery will last 6 to 10 hours for DS games (as compared to 5 to 8 hours for the 3DS).
To cut costs, Nintendo is selling the AC adapter as a stand alone in Japan, but the 3DS XL will work with current 3DS plugs. (Note: in North America, Nintendo is releasing the 3DS XL with the AC adapter.)
Nintendo is packaging the 3DS XL with a 4GB SD card. The 3DS XL will come in three colors (White, Red x Black, Silver x Black) and be out in Japan on July 28 for ¥18,900. The 3DS XL will be out in Europe on July 28. In North America, it will be released on August 19 for US$199.99 in Black, Black x Blue, and Black x Red.