No hold on. Overwhelming numbers and better equipment will give you a good edge over the enemy. The Brotherhood was almost completely wiped out for having the 'better trained soldiers can rambo' mentality. I'm absolutely sure that sure the NCR would give them some kind of different training than just basic training. Sure, they like using cannon fodder, but any organized state wanting to set up a successfull military would teach their troops more than a thing or two.
Then again, the tactics are also a variable. Oliver seems to have an unfortunate Haig mentality, while Caesar seems to be a better tactician.
Yes, but the Brotherhood is not as nearly large as the NCR or Ceasar's Legion. If the Brotherhood had their size like Caesar's Legion then I would think that the NCR would be wiped out. The Brotherhood killed so many NCR troopers without having the ability to mass recruit thousands of men. Caesar's Legion not only larger than the Brotherhood but the common Legionary is probably better equipped to deal with an NCR trooper.
I can agree that tactics is major part of success. Like the Battle of Pharsalus in which Caesar who had 22,000 men defeated Pompeys 50,000. I seems that the Caesar of Caesar's Legion emulates his skill. You saw what happened when Legion sneaked onto the otherside of the Colorado. The Legion destroyed Camp Searchlight, Nipton, and set up base at Cottonwood Cove. Allowing him to effectively shave off the under belly of the NCR.