I think a lot of people are under-estimating Royce.
You just have to look at ,say, Wolf compared to the AVP Preds to realise that bulky muscle doesn't necessarily mean 'better fighter'. Wolf was a lean-mean killing machine...and I get the impression that so is Royce. Dutch is bigger, but Royce is far more ruthless, he'd kill his best friend just to get the job done. Royce left Isabella and the rest out as bait, Dutch would never have left Anna out, and indeed, jeaprodised his own life to ensure she 'got to da choppa'.
What's more, the fact that Royce realised that the doctor was a secret psychopathic killer before the doctor had time to back-stab him leads me to believe he's smarter as well.
Whilst Dutch took the Pred out on his own, he was more used to being part of a team. Royce was a loner who only considered himself. Bad in life, good in battle. ( plus he also took a Pred out on his own ).
It would be a staggeringly tough fight.. but I take Royce just to edge it. I suspect folk are letting their sentimental affection for Arnie cloud their judgement.
Its as simple as this, with how you stated the fight. Head to head or just "knowing" the other was around, no tricks, no weaponary, no sneak attacks(using someone and taking advantage). Royce would never have the chance to use tactics that involves luring Dutch into a trap. Dutch doesn't need traps to win a fight against a human. No weapons, hand to hand, Royce would likely lose to dutch. He didn't display any form of martial art, relied on using other people and all around used terrorist tactics that only help for survivability when you infact have weapons. As far as guerilla warfare goes, Dutch did show that he was capable of making weapons from the natural enviroment. One could assume the same for Royce but we really don't know, at least I don't know. Sure he got the hint about the doctor from Isabella or possibly his self awareness kicked in or ingeneral he just didn't trust the guy or even thought about it while he was running to the Predator ship like a coward that Hey.. why would they bring a bunch of harden killers to hunt, why would they bring a doctor? That for the entire length of the trip didn't display one single hint of caring about anyone but knew a aweful lot about the signs of a paralyzing plant on a alien world.
So lets go
Hand to Hand based on what we know
utch-win. Reasons? He showed hand to hand combat, tried to take on P1, and is a veterned fighter. Muscle doesn't mean everything but someone that is trained to fight and his the agility backed with muscle is more of a threat than a pencil with neither. period. The reason Bruce Lee was so dangerous was that despite being 165lbs, he was nearly 4-6% bodyfat, what you would call "pure" muscle. But he trained for agility and speed. Dutch/Arnold by bodyweight was heavier, yes, but to show the definition that arnold has means he is also low bodyfat. Arnold in his prime was I believe in hte 6-8% bodyfat range or less while competiting. This is a fictional character nontheless, and we don't know his training style but just tossing it out there. Royce all around didnt' display much basic hand to hand combat.
Survivability: EVEN- In truth Royce only survived because he found out what Dutch did from Isabella. So he might have died otherwise, we won't know. so i'm giving it a even. Just because the main character of every Predator movie survives, where as the Predator dies (Even though they're the main characters in our heart)
Tricks: Royce-win. Royce only cared about himself, because he forgot what it meant to be human and to be part of a team (until the end). If they were to use pure trickery tactics, Royce might have had the upper hand since he is a dirty fighter. Dutch was smart and if he evaded said trap or countered, would depend entirely up to the enviromental setting.
Weaponary: Even- Its safe to say that both of them had a vast knowledge in weaponary but the time settings alone would mean that Royce would know more about modern weaponary. Assuming Dutch wasn't still going at it at that point anyway. Giving them the same weapo or even one they don't know, would likely end in a tie or fall back into one of the previous catagories to back their ability. Royce seemed more like a middle eastern themed mercenery where as Dutch wwas more vietnam/korean jungle themed.
In your setting parameters, the match up would be 50/50. If it were to play into trickery/dirty fighting, I believe Royce would win. The way he displayed himselef, seems like the do anything to win type, even using friends and enemies friends to kill the enemy. If it was clean strategy based tactics, I give the win to Dutch as he displayed great ability with trapping the P1 using HIMSELF as bait, his team was just slow to react. but that was more like, you didn't know what the **** you were dealing with compared to seeing every Predator in Predators.
So honestly, its down to whichever character you like the best. But if I had the choice if who I would have guarding my back, you better believe it would be Dutch. I wouldn't trust Royce more than that psycho doctor. Maybe you should have asked who would you pick for your teammate insted? We all know the humans always live, and we all hate it. Because they usually win through some random BS tactic of improbability called a movie script. Not to say that every Predator would have survived their encounter (I think Wolf would have beat his foe, if there wasn't 3rd party intervention) but its safe to say some of our favorites would have survived or should have survived but in these movies they want the humans to have hope.
we know they wouldn't really win however.