Any PC engine over to consoles should be interesting as a comparison, though Source was/is a completely new engine from Valve. I'm actually very interested to see ETQW ported to the PS3, more so Mega Texture and the PS3s memory pools. UE3 to me is representing a new breed of engine that is designed almost specifically to be multi-platform.
Agreed. The lower-res textures in CoD4 (compared to 360) had me worried until UT3 showed higher res textures...though I've no idea just how many total textures either one uses in a level.