Well actually, OutLaw, I would argue otherwise.
My experience and reading indicates to me that JWs tend to leave JWs, not because their beliefs have been refuted, but because the beliefs and practice of being a JW have been displaced by their needs being met elsewhere.
People make new friends, join a new club, meet a new partner, start a new career, move to a new location, or start education. These are the life events that tend to precipitate leaving JWs - other than being forced out.
So if we are really interested in persuading JWs to leave (and I'm not sure we should be, I'm just following the argument through) then the most important thing to do would be to demonstrate how leaving is viable and how others have done it successfully. Logical arguments about doctrine might be intellectually stimulating, not to mention psychologically reinforcing for people who have already left or decided to leave, but don't play much role in the decusion itself.