see thats the only way the Legion gets them if they get a jump on them. The centurions could easily take out a Trooper. But if they caught the VET off gaurd he would probably do a ranger takedown. Then preceed to bring out his ranger sequia and put its barrel to his head while he is laying on the floor for mercey and the VET would say "You Feeling Lucky Punk."
K two things.
1. It is far more likely that the Centurion would have more close-quarters combat experience, meaning they would have all the perks that go with it. They have a chance of knocking the opponent down with every swing, they can't be staggered by melee attacks, they can paralyze the opponent etc. If we're talking about the Centurion getting the jump on the Vet, it's far more likely that the Centurion will have him down before he has a chance to put the gun down and use that takedown.
2. I believe that experience and tactics are far more important than weaponry itself. In both battles of the Hoover dam, the Legion shows superior tactics: they get the jump on the NCR time and time again, DESPITE running around with hammers and shotguns when their opponents have sniper rifles and automatic weapons. The only reason the first battle was lost was due to a massive mistake made by the Legion's general himself whereas the NCR commanding officer made a brilliant one: the loss was specific to two men and the decisions they made, beforehand the Legion was winning. The entire game is filled with quests showing the NCR being unorganized and unprepared, whereas the Legion only has a couple tasks to ask of the player, generally ones they themselves could take care of alone. The tactics used by the Legion in the Second Battle show that they are VERY well aware that they're at a disadvantage when using hammers against snipers, and they show they can adapt to this. For these reasons, I'm arguing that a Legion Centurion is probably more than capable of creating/using a situation to get that jump on the NCR vet. The NCR vet on the other hand, if placed in a situation that is more favorable for the Centurion (AKA, close quarters combat), isn't going to be able to do much.
The Centurion and the Legion are constantly thinking, finding new ways to handle issues. The NCR on the other hand only stays the course: they don't adapt. I would argue the experience and the ability to adapt that the average Centurion shows are far more important than having a sniper.