text: what are the difference between greek orthodox and catholics? in terms of doctrine or things that actually matter like how often you need to go to church, christmas, and etc.  essentially anything that would affect family life. between the eastern orthodox and the roman catholics??  isn't one of the main differences that most roman catholic priests are not married and most eastern orthodox priests are permitted to marry?  -- i think that "would affect family life".  another difference ... roman catholics acknowledge the supremacy of the roman pontiff; eastern orthodox do not.  similarities include, i think, that they all believe in transubstantiation.