Here is how I break it down:
If the situation involves a fixed number of Predators inside an Alien hive, who chooses not to (or cannot) escape the hive, then it's merely a matter of time until the relentless swarm of Aliens overwhelms the Predators. In this situation, the Aliens pwn the hardest.
Aliens - 1
Predator - 0
If, on the other hand, the situation involves an open-space, where the Predator run freely and use vertical space to his advantage, he can probably blast Aliens all day long with his laser-cannon before anyone of them get close. Then again, I don't know - maybe even there, the Aliens could still get him, given enough time. They're some clever, cunning, relentless motherf**kers. It's possible. But the Predator certainly has the upper hand in this situation.
Aliens - 1
Predator - 1
When we're talking about 1-on-1, up-close combat with no use of weapons, then the Alien has more advantages. They are simply designed to be the most naturally dangerous organism EVER. They have like, a 15 ft. long tail that will easily penetrate a Predators body. They're strong as hell. The Alien that penetrated the Predator with its tail, even lifted the Predator with it. They can spit acid and melt their victim's existence. They can tear shit up with their claws, and get really nasty with their secondary mandibles. And this is just the ordinary, standard drone based from a human host we're talking about.
Aliens - 2
Predator - 1
Aliens win, 2:1. And THAT, is why the Predator considers them the "Ultimate Prey". Because they know they're HARD to beat.
