There was a point at which a clear line between the various Christian sects was apparent. Back when Martin Luther wrote his apologies it was clear what his dissents were and many followed.

With each separation there were further doctrinal dissents. Eventually, the separations began to include NEW doctrine.

Soon we saw the evangilist and NO doctrine, but the voice of the person who claimed to KNOW the truth. Of course there is a hidden doctrine, it exists for the purpose of tax exemption only.

Finally there came those who wanted in on the action and so they proposed unity doctrines, to gather in the stragglers and the confused.

So the answer to your question is that the differnces lie withing the doctrines, which I would venture to say that only 1% of any particular congregation actually know what that doctrine declares.

Those that do know thier own doctrine, could not tell what separates them from all the others.

If you have a couple weeks and a lot of patience, you can find most doctrines posted somewhere on the internet.

It's a tangled web at best and since it means nothing to those for whom it applies, they are not too discerning or revealing.

So good luck with that!