I feel like every time someone is asked to explain the difference between Sunni and Shia, people give the same incredibly unsatisfying answer about the schism arising from a disagreement about who Mohammed's designated successor was.

No one ever seems to answer with the thing that people actually want to know, which is "What are the differences between these two groups *today*?" I'm not even sure I know the high points of the differences.

It seems to me that Catholics and Protestants are fairly easy to compare, with the most broad-brush explanation of the differences being that Catholicism has a strongly hierarchical arrangement of religious authority while most Protestant denominations have more decentralized authority. They disagree on a bunch of minor bits of doctrine that probably most people don't care about, the big differences are around the culture of religious authority and the degree to which rituals are formalized.

Is there an equivalent comparison for Sunni vs. Shia? Or is it more like asking people to compare "People from Canada" with "People from the US", where there are a bunch of small differences, and Canadians in particular don't like being mistaken for Americans, but there's no overarching theme to the differences, it's just slightly diverging cultures.

Or, sticking with religion, I feel like maybe the Catholic church vs. the Orthodox church might be the Christian version of "US vs Canada", since I get the impression that the Orthodox church is similarly hierarchical with highly formal rituals, but the hierarchy and rituals are slightly different (they even do their holidays at slightly different times).