Someone mentioned something about military training being the most effective.
Short answer: No.
Longer answer: The military trains you to fight in a specific manner, like any martial art system. It's the reason why even fighting luminaries like Miyamoto Musashi always encouraged learning from different arts. Whether the legend surrounding his swordsmanship is real or not, one cannot ignore the fact that even the supposed "greatest swordsman" would encourage fellow fighters to look at how other schools do things, if only to learn more.
Military training trains its soldiers for the reality of their world. That's guns, knives, and bombs. So it's likely that their hand-to-hand skills will be minimal. This isn't to insult soldiers, or claim that they cannot fight. In truth, a soldier, with confidence and strength, is still very likely better than your average moe. However, they aren't trained boxers or grapplers, no matter what they say. Even bootcamp, despite it's hardcore philosophy, is still more geared towards breaking doubt in their minds and programming them to assert themselves on the battlefield. In short - they're not uber-mensch. They're just men like anyone else.
Kurt Angle would probably due pretty well against BJJ, but only because he too has knowledge of grappling. I don't like to think of BJJ as the uber-art. What makes BJJ so successful is that it is, or at least was, a technology of fighting that had largely been ignored in the era that fighters lived in. What, with wars focusing largely on sticks, swords, knives, bows, and finally guns, why would anyone really focus intensively on anything EXCEPT striking? BJJ comes in with this radical concept... what do you do without all of the extra stuff? People that are just strikers fail not because their punches don't work, but because punches and kicks aren't all there is to fighting.
So I say, who cares if Kurt Angle could last in a BJJ fight. Of course he might. He's a grappler.
Looking at today's evolving fighting arena, you'll be hardpressed now to find a "pure" BJJ fighter in the professional ring. BJJ started a trend for fighters to learn grappling. But now, grapplers need to leanr striking as well to succeed. I know Royce and Rorian have tons of notches under their belts. They paved the way. But it's very unlikely these days for them to succeed against the new breed of fighters with just grappling skills. They too need to know how to punch, how to clinch, and all of that.
If you're looking for an art, find something that has solid striking and solid grappling. You don't need to be a super expert to be successful, especially in every day life. Unless you plan on competing, it's not critical that you get the very best training.
