First, go here to compare: BlackBerry - Compare BlackBerry Devices | Wireless Handheld & Mobile Features Comparison From RIM
While some of this has been stated before...
- The 8310 has a Camera (none on 8800)
- The 8310 comes with a built in Spell Checker (not on the 8800 - yet?).
- The keys on the 8800 are funky but a tad larger than the 88310's, but the keys themselves are nicer on the 8310 (personal opinion).
- The Curve has a standard 3.5mm stereo jack - the 8800 uses a non standard 2.5mm jack (both for stereo and voice on both devices).
- The Curve has Stereo Bluetooth - not available on the 8800 (and probably will never be available).
- The Media Player on the 8300 is a bit nicer than the 8800 (don't know why it shows as not available on the comparison chart but I'd imagine it's at least the same one that's on the 8300!)
- The rated battery life on the 8800 is rated to have about 25% more battery life than the 8310 (because the battery is about 25% larger - but not too large or heavy)
In short, the 8310 is a much nicer device. However, I have an 8800 and love it, and wouldn't give it up for anything less!