This got kinda long - CN at the bottom.
First off - I'm not a psychologist, and I have no formal training in the field. I've also had absolutely no success in waking up my wife, so take this for what it's worth. I thought this might be a helpful perspective for some, though, so I hope someone can find it useful.
I read an article (here's one on the same topic) years ago about decision making being emotional not logical, but didn't give it a tremendous amount of thought. My therapist recently referred to the idea that came from this study and I've been thinking about it off and on since. It turns out that no matter how much we might protest that a particular choice we made is based on well thought-out logical arguments, if you dig deep enough there is an emotional motivation. In reality, the typical decision making process goes like this: decide what you want based on emotion, then rationalize the decision with your powers of reason.
In my case, it was nice to believe that my decision to stop being a JW (as well as the many decisions that lead up to it) was based firmly in reason, but that's just not the case. I'm not suggesting that the JW cult is all that it claims to be, nor am I suggesting that it's a better life to live as a JW. What I am saying is that it's just not as simple as "It's not 'the truth' so I'm leaving." I'd logically decided long before my awakening that god was not necessary to explain the world, and that it was entirely possible that he didn't exist. I actually liked that idea better - evolution and cosmology have such elegant solutions to the problem of our existence when compared to "god did it." Why, then, did I not leave in my late teens? I hadn't yet found a reason to leave that was based in emotion.
I was uncomfortable lying or misrepresenting the truth, and that made me uncomfortable with the cult because I could never explain my involvement to anyone that found out that I was a JW without either resorting to misrepresentation/lies or saying something like "it makes sense, I'm just not explaining it well" to end the conversation. This emotional discomfort with untruth was what lead me to have a desire to know what was true. That desire lead me to research outside information in spite of the phobia indoctrination. When I did, I pushed past the child abuse scandals, the 607 stuff, the critique of the watchtower's use of circular reasoning, on and on. Don't get me wrong, all that stuff disturbed me deeply, but I didn't have enough of an emotional connection to it for it to cause me to make a decision. Then I found black-and-white proof that I had been lied to. There is at least one statement in the creation book that can be characterized in no way other than an outright lie. There are several that are, at best incredibly hypocritical (quotes taken out of context, etc) and hypocrisy is another thing that I absolutely loathe (another reason that I was uncomfortable with JW beliefs and rules). That did it. My emotional abhorrence of lies and hypocrisy woke me up, not my powers of reason.
I often see people on the forum making suggestions that essentially boil down to "explain logical flaw x in doctrine y and they'll have no choice but to wake up!" Unfortunately, that's just not how it works. For someone to wake up they have to see being in the cult as a violation of one (or more) of their core values. Some people just don't care that much about absolute accuracy/truth/etc as I do, so they can look at the same lie in the creation book and say "I guess that just doesn't matter to me that much" (paraphrasing one of my wife's responses). People without children might hear of the child abuse and it doesn't hit home enough to matter. People who are comfortable with hypocrisy can be elders and enforce rules on the R/F that they know would not be applied to them due to their rank, and it doesn't bother them. People who feel that their connection is with god and claim to take everything the cult says with a grain of salt can learn of the false prophecies of the past and say "they were just harmless guesses, everyone knows that 'no man knows the day or the hour.'"
It seems to me, if you really want to wake someone up, you have to know what drives them. What's their emotional connection to the cult? What emotional reason would be enough to cause them to rationalize leaving? That's the only thing that will do it, not cold facts and logic. Knowing this could completely change your approach to waking someone up. What woke you up won't wake up someone else because they have different values. You may be an expert on 607/587 and it may be trivially easy for you to prove the dates are wrong and therefore prove that the org is a false prophet that was never appointed by god. There's black and white proof that can't be argued with, but if that proof doesn't hit someone at their core values in a way that creates an emotional need to leave the cult, then it will do nothing. On the other hand, if someone values love above all else, the considerably more subjective evidence of a lack of love in the congregation may wake that person up in a heartbeat. In this case, it would only be after the emotional reaction to the lack of love that this person would care about all the facts and proof that it's a cult. They've made their decision, and now it's time to rationalize it. Up until that point their decision was to stay, so they weren't interested in information that they can't use to rationalize that decision.
Unfortunately, getting at someone's core values and motivation isn't as easy as you might think. Most people aren't aware of their core values, or certainly not all of them. Least of all cultists, because they've had the cult's core values superimposed over their own. For me to have the realization of my true motivations for leaving it took about a half hour of questioning by my therapist wherein he essentially played the part of a kid asking "why?" over and over again (there's a bit more to it than that, but that's sure what it felt like). Getting to really know what makes them tick at the deepest level will probably give a much better chance of waking someone up than simply disputing doctrine or showing evidence of a lack of love, or what have you.
I think this difference in core values combined with differences in first-hand experience with the cult is what ultimately makes it easier to wake up some than others. People who value truth, love, justice, etc are probably more likely to wake up than those that value duty, loyalty, or honor. That's not to say that it's impossible to demonstrate that the cult is disloyal, but depending on someone's experience in the cult it could be considerably more difficult than demonstrating that the cult is dishonest. Also, I suspect that it's infinitely easier to wake someone up if you share a number of your core values - in this case what woke you up will probably work for them, and making the case in a way that affects them will feel much more natural to you.
Cliffs Notes: Decisions are made on a purely emotional level. If you're going to convince someone to do something (like leave the cult) that they're reluctant to do, you have to hit upon their core values and something that motivates them on an emotional level. It's only then that they'll be interested in information that supports the decision to leave, because it's only then that they'll be actively trying to rationalize that decision. If only it were as simple as pointing out the flawed logic in one doctrine cults wouldn't exist.