CONVERTING TO CHRISTIANITY: Messianic Jews convert because they believe the Jewish prophecy of a messiah was about Jesus. Rabbis, experts in their own religion, experts in their own Hebrew language (which is not the same as old Hebrew which was wiped out by detractors), and experts in their own prophecies, reject the notion that Jesus fulfilled the Jewish prophecy of a messiah. Many had claimed to be the messiah. One messiah wannabe was a thief named "Jesus, son of God." (or Jesus Ben Abbas in the Hebrew language). He was slated to be crucified instead of Jesus, but let off. Ancient Jews, in the days of Jesus, had heard the rumors of Christ's miracles, and merely assumed that he was a sorcerer, and, therefore, evil.
CONVERTING TO JUDAISM: Surely everyone realizes that there are many denominations of Christians today, and there are many "conflicting" versions of the same New Testament. These converts wanted to learn the real religion before it was rewritten by human kinds or human priests, and, like Reverend Melissa Scott, seek to find truth in translations of ancient Hebrew and Latin texts (and occasional Greek and Arabic).
CONVERTING OUT OF AMISH: The Amish life is austere. Women have to be stuck in the kitchen all day doing drudgery, and they believe that idle hands are the tools of the devil. They will occasionally use electronic gadgets (phones, recorders, etc.) for office work, but, at home, they practice strict avoidance of modern devices. Many young Amish leave the religion and home, and seek a wild life (including prostitution), then are accepted back to the Amish life (which they are allowed to do only once in their life.....if they do it again, they are ousted for good).
CONVERTING TO MORMONISM: Mormons assert that Jesus wasn't restricted to just the middle east and eastern Europe, but made his appearance in North America (and perhaps other places as well). That seems like a very logical and likely idea. The Mormons have their own bible. It is most compelling that they reject war and killing (remember, God said "thou shalt not kill" and they attempt to follow God's teachings). Mormons don't drink, gamble, nor even drink coffee. Mormon and Amish people are very healthy, and many believe that their plan for living is a good one.
CONVERTING TO VOLCANO GODS: Well, there it is. While Christians have a very hard time proving that their God is real, volcanoes erupt with fiery melted rock, and their presence is impossible to ignore. Their God is real and tangible. I can't visit, because I'm afraid to be sacrificed to a volcano God (they toss in the best food and best people).
CONVERTING TO ANIMISM (VOODOO): They believe in making zombies of living people, and animating the dead. They use voodoo dolls and strange chants and ceremonies. I sometimes lose debates, and wonder if they could spare a voodoo doll.