I'm actually gonna guess H4 is the "mess maze," given everything. There's not actually that much substance in the movie (Michael kills a police officer and service guys off-screen and only really kills people onscreen in the last twenty minutes) and you move between different locations - a police station, power station, both levels of a two story building along with the attic and the roof, then a school and a highway for pete's sake - a ton, which means awkward transitions.
Meanwhile, there's not that much blood in the movie (only real big blood sequence is the shotgun kill and I guess the police station?), whereas Unfriended is practically marinated in blood, so I'm guessing that's the gory one. Meanwhile, First Purge is apparently gorgeous, and it's really hard to screw the Purge up, so I'm guessing that one's in the safe zone.
EDIT: Plus, apparently Orlando's H4 isn't looking too hot either. I think it's just a hard movie to translate, really.