A member on the gaming forum Neogaf wondered which version of The Elder Scrolls V: Skyrim yesterday's new trailer had been captured on. Bethesda's community boss Nick Breckon stepped in to clarify that "all of this trailer was captured on Xbox 360. Also, the draw distance is not faked in any way."
From which we can draw two conclusions - it would seem like the Xbox 360 is the so-called "lead version" and that we really want to see what the game will look like on a powerful PC.