The way I see it, the smaller the crew aboard that ship, the less chance the predalien has for survival. If there were less preds, then missing "personell" would be noticed alot faster, & the predalien wouldn't have claimed as many lives. But really, think about it, if one predator is more than a match for an alien in close combat, then what chance would a single predalien have on a ship containing well over a hundred of them? (I'm going to ignore the fact that the predalien would turn a captured host into a superfacehugger egg etc. for now)
It's not like the predators are helpless lambs waiting to be picked off. If the predalien made the slightest move at the wrong time, it would get it's head taken off, it would barely be able to turn anywhere without practically running into a pred. A predalien is not some god-like killing machine, it is basically a drone with more developed musculature, making it physically more powerful, & a few predator cosmetical changes, ie: mandibles. An experienced predator can finish off an alien in close combat in seconds, & even occasionally a youngblood can kill an alien with no problem in a fight (see the pyramid flashback scene in AVP, the predator to the left skewers an alien on his armblade & kills in instantly). So if a predator
can kill an alien in close combat & on occasion doing it with ease, a sole predalien on a ship with well over 100 predators would stand very little chance of survival for long.