Question: Why are Lubavitch and Breslov so popular with baalei teshuvah?
Answer: Their rebbes are dead.
In case you're thinking that I have a sick sense of humor, here's my logic. Both Nachman of Breslov and Menachem Mendel Schneerson live on in their writings and in the stories told about them by their Hasidim. And, needless to say, these stories tend to skew very positive. After all, who is going to say that their late, great Grand Rebbe is a schmuck? And, since they are deceased, none of their actions can belie their reputations. Unlike say, Satmar or Bobov, where the movement has split along which of Reb Yoelish's or Rabbi Halberstam's descendants is actually the true Rebbe, and which is the wannabe (isn't this what split the Church into Catholic and Eastern Orthodox factions?), or Skver, where the Rebbe may or may not have sent his houseboy to burn a guy's house down (this actually happened), all we have to go off of are memories. And acharei mos kedoshim, these memories tend to emphasize what a nice guy these rebbes were.
Lest you think I am needlessly picking on Hasidim, I have to say that the Litvish are no better. In fact they are often worse. Far, far worse. Fail to toe the party line, whether you are Dov Lipman or Avi Weiss, and you find yourself on the receiving end of wrath bordering on excommunication. The roshei yeshiva are quick to cast out the "other," even if this "other" includes their own colleagues. At least the Hasidim, who have central leadership, tend to leave other Jews alone.