Part-time host has other jobs. He may be a teacher, a host or a reporter. He only works as a part-time host in his spare time. Full-time master of ceremonies is a job and has been a master of ceremonies.

Actually, I have been to several weddings. In reality, part-time hosts are literate and capable. For example, a teacher who is a master of ceremonies is better than a full-time master of ceremonies in a wedding company. The full-time emcee of the wedding company is simply too grounded.