Oh. Well I lost my 64 copy. And the 360 version still uses the 64 bit graphics from the original 64 game they just polished them also the campaign is the same.
Well I think they wanted to keep it as close to the original as possible because that's what the gamers fell in love in the first place. But I don't work for Microsoft so I don't know.
Perfect dark n64 is the best
Perfect dark zero is in the middle
Perfect dark x360 is the worst