Desktops are always better for gaming.
Video editing takes up A LOT of Hard drive space, if it doesn't then your essentially not doing it right ahaha!
Your going to want an external Firewire hard drive, get a like 200GB Drive or something so you can have fun and use special effects. The DDR is nice, but Im guessing since its a newer system you can upgrade it to at least 2GB if not 4GB of RAM, DO THAT FIRST!!!!!
Also, when you first boot the computer, go into the BIOS Settings and disable the power-save settings for the CPU so it will run at its full potential (Just leave it plugged in) Or else your going to run at around 2.4Ghz instead of 3.0Ghz