Bethesda engines steaming,level of detail system always looked crappy to me,but...
PS3 looks better in those pics.
One explanation is that they use hdd as a cache even if you install so the drive has to stream everything and write at the same time.
It wouldn't surprise me if disc beats hdd,in 360 case.USB might beat both,who knows
Interesting fact
360 install is 3.8 GB,PS3 mandatory install is 5.5GB