I think the Preds are supremely dangerous even unarmed..they're just that wily, vicious, strong and tough. I figure they probably evolved from a naturally dangerous, aggressive creature before they invented their technology anyway. I also look at the films and they show that the Pred likes to get into close quarters a lot so it's not as if he's merely a long-range assassin. I can see the Pred manhandling the Xeno to be honest with you. So, while stripping the Predator of his tech would definitely narrow the gap between the two species, I would put my money on the Predator most of the time, but it would be exceptionally dangerous and if the encounter was played out 10 times I'm sure the Alien would win some of the time.