I think the body on the alternate Fifield monster looks nice and menacing but the face/head looks like a horribly conventional grey alien. The more I see of the alternate version the less I like it. At least by showing him earlier in his mutation it leaves more to the imagination and doesn't seem to represent something that mixes up the alien metaphor even more (knuckle walking like a gorilla? What the hell?). That face is not as threatening. I do think the concept sculpts for this version were a bit better and more original while feeling more of a tie to the alien.
Ultimately I think Ridley's instinct to go in-camera is always better. It's always more believable.