RAGE to have 8GB install for PS3, and 3 discs on 360.

[Reasonable]

Whichever way you cut it the engine is designed in a way you want to have HDD speeds and not BR or DVD. Id have made it clear they advise installing on 360. They've used the fact PS3 has an HDD guaranteed to go the mandatory install route on that platform and of course you'll install on PC.

Without installing its clear you're looking at texture pop-in and reduced performance due to the design of the "mega texture" assets.