I'm terribly curious as to whether either of the church splits you've seen were over teaching or egos. In general I've found it's always the latter, sometimes dressed up as though it were something more objective.

In any case, it isn't fun. I once served a church that had gone through several splits and was assured that the fighting was over, that everyone remaining was on the same page. This was true, but it was a deeply dysfunctional bunch, and it was that church that got me out of full-time ministry and nearly broke my faith in the process.