Well both are strong aliens. Aliens are not pure muscle. They are alien beings , they might not need muscles just like some creatures on earth don't. Maybe they rely on a form of building up pressure which leads to a high velocity , say , pounce. As for Predators , they are strong creatures. They are physically huge and capable of doing huge powerful moves. A Predator can jump huge spans in Predator 2 , they also can swing aliens by the tail easily. aliens are strong too , perhaps slightly stronger. But they are in no way the by far , stronger species. A predator bare handed would lose to an alien. Still though with a combistick at close range I'd give the edge to the predator - slightly.