I suspect the shunning mandate is the major difference. The Mormons were smug enough to actually think they were right and wouldn't need any further shackles. Now with the latest church admissions on hot topics the core members are either hunkering down into extra committment mode or leaving.
Yeah, that's what I was thinking... I know mormons do occasionally shun those who leave, but I thought it was more them being super self righteous, not something they did to avoid being shunned themselves, like it is with the JWs.
Mormons also encourage higher education. In the past that probably didn't hurt them too much, but as the world gets more and more secular that's going to cause problems.