It's the original dude for me all the way, as it just worked both visually and emotionally, this twisted creation of a creature that gestated in a man, literally Kane's son. Filming limitations and costume restrictions may have forced some of the shots to be consumed in shadow and darkness, but even when you see the full costume it's still really impressive; I just couldn't imagine it looking good if they filmed a shot of, say, Bolaji running down a corridor chasing after Weaver. That'd be classic 1950s B-movie material and they may as well have had them chasing a painted beachball.
I also liked the Isolation merging of the original and later designs, same head and chest, different from the waist down. It made sense for the game, the way it twisted out of vents and such. Could you imagine if they had stuck with the full design of the original creature when you could see it full-body walking around? It would have looked ridiculous so they not only made the right decision in design it was right for the game, too.
