I think in this case you mean different
from. "Than" would imply that Scientology and Mormonism are different (from something else, i.e. standard religions) and FSM is no
more different than they are. At the very least, "than" would require a modifier like "more" or less to indicate a side (like you could say A is ugli
er than B, but not "A is as ugly than B.")
Are you sad you asked?
Edit: regarding Dana's post, "different to" is entirely a British idiom.