I don't know. The preds have the advantage of stealth unless it's a jungle-like setting, in which case the multiple pred vision modes would give them an advantage as well . The shoulder cannon can be matched by the wookie crossbow, in which they're all extremely proficient. One blast from the shoulder cannon should technically be the same as a blast from the shoulder cannon. If it comes down to H2H......i don't know. I've seen a predator grab an alien by the tail and smack him against walls, and i've seen H. Ford say a wookie could tear your arm out and beat you with it (or at least my sick distorted mind remembers it that way). However, i'm leaning towards the predator. Better weapons, better stealth technology, better detection skills, and possibly better fighting skills (most likely).
Don't see how that would really be of importance. You really couldn't say the wookie is more experienced having been older. That would normally work, but not against a predator.