Battery Life: The lowest brightness (15-19 hrs), low brightness (10-15 hours), high brightness (7-11 hours), highest brightness(5-8 hours)
Software: Software for Nintendo DS, Software for Game Boy Advance
Input-Output: DS card slot, Game Boy Advance cartridge slot, AC adaptor connection, stereo headphone/mic jack
Processing Power: MB RAM, 67MHz Processor
Also sorry about the funky layout. Over 2000 characters.
DSi Battery Life: The lowest brightness (9-14 hrs), low brightness (8-12 hours), medium brightness (6-9 hours), high brightness (4-6 hours), highest brightness(3-4 hours)
DSi Software: Software for Nintendo DS, Software for Nintendo DSi.
DSi Input-Output: DS card slot, SD memory card slot, AC adaptor connection, stereo headphone/mic jack
DSi Processing Power: 16MB RAM, 133MHz Processor - The DSi runs slightly faster than the Lite do it faster processor and more RAM.
DSi Extra Features: Two VGA Cameras, built in Music player, Access to the DSi Shop, downloadable Web Browser.
Size of Liquid Crystal Display: 3 inches
Liquid Crystal Screen: Possible to display 260,000 colours
Portable Size: Width 133mm, Length 73.9mm, Thickness 21.5mm (touch pen is approx. 87.5mm in length)
Power Supply: AC adaptor for DS Lite
Weight: Approx. 218g (with touch pen and Game Boy Advance cover)
Charging Time: Approx. 3 hrs
I'm just backing up Calums point about the DS Lite being the better of the three DS. It has a GBA slot if you have various other GB games which the DSi does not. Below I've posted the differences between the two consoles.
Size of DSi Liquid Crystal Display: 3.25 inches
DSi Liquid Crystal Screen: Possible to display 260,000 colours
DSi Portable Size: Width 137mm, Length 74.9mm, Thickness 18.9mm (touch pen is approx. 92mm in length)
DSi Power Supply: AC adaptor for DSi
DSi Weight: Approx. 214g (with touch pen)
DSi Charging Time: Approx. 2 hrs & 30mins