ADI's previous Predator designs had aspects that made them look outright fake, especially in comparison to prior iterations in Predator and Predator 2 particularly or even Predators' Berserker, Prey despite the design departure does not have this issue.
Simply put: Scar, Wolf, Crucified, Fugitive, look bad with the mask off... whether that's being goofy looking by widely missing the mark at attempting being a handsome looking alien fellow, (see Garrus Vakarian for a good example) bobble headed, being apparently slack jawed, rubbery looking, having multiple skin folds around the mandibles or all of the above.
Scary boy:
Handsome boy Garrus Vakarian:
Feral looks good with the mask on but just looks different with the mask off. He does not have any of the above type of issues that take me out of the film. His crime's being ugly.