The PlayStation 3 version has a mandatory install of 8GB before you can play, where as Xbox 360 can optionally install it for a whopping 22GB of HDD space.
The newer console models have plenty of HDD space to go around but for those still milling about on the 40GB or 60GB SKUs it can prove more difficult to play new games on PS3. Still this is nothing new to us PC gamers who have to install everything.
Rage releases on Xbox 360, PS3 and PC October 4th in the US, 7th in Europe. Xbox 360 can optionally install game data for better performance or simply run it from the disc.