Not sure how much math is needed. Humanism is better in a vacuum, while religious is better when you have a specific reason for it.
- If you go reformed, the +2 and the cb vs basically everyone without exception makes religious a must-have.
- If you are orthodox, byz especially, you want to paint the map your true faith so humanism makes little sense.
These are the two situations where I don't see why you'd take humanist over religious. The rest are up to debate. If you are catholic, you may want it to stack totf base and the +2 bonus. I consider the points for a catholic weaker than for reformed, but they're something, so that religious vs humanism becomes a real question. The CB doesn't usually appeal to me since it's not going to help me vs the big powers / colonizers, and without the best part of the idea group being put to good use, I can't justify it at least in single player. I don't think I ever take religious as a non-Christian. Not sure of the point really. I mean, maybe if I plan to convert at some point?
So yeah, there are definitely cases (orthodox and reformed) where religious just seems far and away better, but by and large I can't see without a specific application how it even comes close to the same advantages as humanism in some general/abstract math without specific applications.
My most recent games I went neither. I failed both times, but not due to unrest, and am not sure either (or both) would have helped in any way. Humanism seems to end up just giving me less LA, more or less. Religious without making heavy use of the CB etc. strikes me as a waste of an idea group.