"There are two paths through a career like his." - This is the exact definition of a reductionist argument. I don't believe every IT guy working in the intelligence industry much choose one of the two paths you outlined. Is it perhaps possible that some of them could be doing what they do with a clear conscience, and actually believing in what they do?
Snowden sees some Swiss banker shmoozed up and boozed up by a CIA agent, the banker wrecks his car, ends up being recruited (approximately what is described in the Guardian article.) Snowden is aghast, it sounds absolutely terrible on the face of it, no? Uhh, maybe? If in the end, billions of dollars of international criminal transactions are exposed, which closes off a safe haven and laundering mechanism or all kinds of 'bad guys' around the world, who is to judge the real moral value of the outcome?
I'm going to go out on a limb and say some IT/security guy operating at the periphery of the enterprise simply doesn't have the full story. He doesn't have the full perspective to make that call, not for all of us. If he witnessed specific things that bothered him, there are other ways he could have attempted to address it first. He should have gone to the inspector general. He should have gone to the CSC. He could have approached Congress. In truth, by his own admission, he did none of these things.
"Thankfully, all it takes is for one to blow the whistle" you write. I think it is worth turning that question around. If thousands of people are engaged in this enterprise, all of them also acting earnestly and also possessing eyes and consciences, what gives Edward Snowden the right to presume his moral judgements are more correct than everyone else's? It seems to me a particularly self-aggrandizing and hubristic act.
At least Bradley Manning had video footage of innocents being killed. All Snowden had was some powerpoint slides he objected to.