They had "Old Painless". Nuff' said right there. If you can take down Old Painless, you can take down a Pulse Rifle. They also had gernades, machine guns, pistols, knives, machetes, and a whole lot of other stuff. Plus, these guys were REAL tough guys. They could fight someone hand-to-hand and win. The only one I saw REALLY to that in Aliens was Vasquez. In addition, the marines from Predator could:
1. Keep their heads on in scary situations. Even after there were several deaths, they kept it together. Even when Dutch was the only one left, HE kept it together. The marines from Aliens broke down into fits of "GAME OVER, MAN!" when the situation got rough. There was only one break-down the entire movie that I remember.
2. Use their brains. They used stealth, cammo, traps, and SHUT UP when the Pred was around. They worked together and thought about the situation before running in half-cocked.
Besides, this is an entire clan of Predators. They'll use stealth just like the Pred from Pred 1. The marines are gonna take a few down, but they're still screwed.
EDIT: ANd there in nothing I would like to see then Mac and Poncho beat the out of that whiny little wuss, Hudson.