My money would defenintly be on the preds. Most ppl forget that even youngbloods have probably been training to hunt & fight for well over 100 years. Even an unblood is capable of taking down an alien with relative ease (just look at how badly celtic was beating grid's @ss in AVP, up until the end of the fight when he got overconfident) now, these preds are youngbloods, so they r more experienced, now, put 6 of them against 2 aliens, & there's gonna be a whole lotta smack getting layed down.
Yes, the predalien would maybe be able to fight off 1 or 2 of them, but against all 6 of them, even with the runner helping (as powerful as runners are), the preds would simply tear them apart.