Basically if you want a decent CB against same religion guys you have to be a horde now.
Hordes also deal with corruption pretty well due to razing, and main issue with playing horde with 'standard' ideas (big religious unity problems) has been neutered.
Finally, if you get bored of being a horde, you can go Christian, reform to Eastern, then instantly hit Western focus. This is what I intended to do, but I realized that even with nerfed razing having alternate means of monarch point generation is not something to be thrown away.