So much ignorance it would almost be funny if it weren't so sad
Christianity is a religion, whose beliefs are well publicised and freely available to everyone. Anyone who wants to can join, anyone who wants to can leave, people are promoted up the religious hierarchy on merit alone.
Scientology on the other hand is a cult, you have to pay money to join, you will find it very difficult to leave, members are strongly encouraged to progress up the hierarchy, which will cost you even more money - to all intents and purposes, scientology is a pyramid selling scheme. No-one really knows what scientologists believe in, because this is only revealed as you progress up the hierarchy. Any attempt by former members to publish what they believe in is quashed with copyright laws, yes, copyright laws. The scientologists seek to actively persecute critics, see for example the case of Keith Henson.