From what I've read, the 6 GB install is the PC version, the higher res textures take up more space. According to Todd Howard from Bethesda we shouldn't be worried, it's just better compression techniques. Still if the 3,8 is correct that's really tiny.
Ah well it's an Elder Scrolls game. I'll give them the benifit of the doubt, eventhough 12 GB across 2 discs would have been more reassuring ;)