Just on the face of it, I'd probably go with candidate A, unless:
Was candidate B in some sort of technical program? Even if not a nuke, was he in an engine room, in HVAC, a missile tech, an electrician, a jet engine mechanic? Or, was candidate B a MAA, or combat engineer, corpsman, or DK? See the difference? If our military person has experience in pressures, temperatures, powers and flows, heat transfer concepts... valves, heat exchangers, electrical and electronic components, even if it is on the micro vs macro scale, then he's going to do well on the POSS and mini GFES.
I sense the bias in your question regarding college kids with degrees, and maybe there's some basis to regarding someone who spent 4/5 years living the fun life, getting average grades, but getting a degree as having an unfair advantage. But, I think that's the reality that you'd better face. As an employer, I don't really care how many MIT courses you audit in your spare time... It'll just make you do well on the mini-GFES/POSS. That's all the credit you get for it. If I have 2 people, and one has his Calc I course done, with a C, but the other reads Calc books as a hobby, who gets the credit?
Stacey, I'm not sure if I'm saying this clearly, but a college degree counts against a whole lot of experience. A lot of those HR postings have those tradeoffs... 10 years experience, or associates and 6 years experience, or BS and 2 years experience. That's just the way it is.