Alien > predator
first encounter:
preditor camo is useless and aliens are invisable to the peditors heat vision = dead preditor before he even knows alien exists.
after preditor learns he cannot see his prey with his helmet:
predator is a solitary hunter, aliens swarm on thier prey, and in close combat acid for blood, mindless animals with a need to protect thier lair and feed vs. solitary hunter = still dead predator.
i know it's stupid to argue over but "if the shoe fits"