Military armorers vary in skill, depending on their level. Some are parts swappers. Others are fully trained in some areas of gunsmithing (note: gunsmithing tends to become specialized nowadays and there are some guys who do nothing but build rifles, others who work on particular handguns, some who do nothing but shotguns, repair specialists, engravers, blackpowder rifle builders, etc.). I know one gunsmith graduate who enlisted into the Army and was promised a billet in the Army's Marksmanship Team as one of its armorer. He had to attend boot camp first.
Schools are a good place to start and their graduates vary in the level of skill and knowledge. As to which is best, that depends on the skill and adeptness of the individual student too. Some students are just better than others (therefore the worst graduate from the best school may not be equal to the best graduate from the worst school).
Gunsmithing school graduates are probably best off seeking employment from others. First, no one really graduates as a "master gunsmith" and are really only journeymen upon graduation. Second, by working for others, they don't have to start from scratch including developing a business plan, getting a loan, develop a marketing plan, developing a client base, etc. Instead, when they work for others, they trade their labor for money. So, while they work for someone else, they can accumulate experience in the field and build up capital for their own enterprise. BTW, there is no shame in not having your own business. Some folks just aren't businessmen and there are plenty of good gunsmiths who work for others.
Vigilantibus et non dormientibus jura subveniunt. Molon Labe!