I asked this on the Eastern forum and wanted to ask it here also. “I know this has been asked many times, but I am preparing an informational series on Church history to be used for RCIA and other events. My question is what separates or are differences between East and West. I am looking for the big issues. thanks in advance for any information that can be provided so that i can properly present the information. Peace”
A good place to start is this article: https://en.wikipedia.org/wiki/Eastern_Orthodox_%E2%80%93_Roman_Catholic_theological_differences
Two good books to read are: The Orthodox Church by Kallistos Ware and The Early Church by Henry Chadwick.
The REALLY big issues are universal papal jurisdiction and papal infallibility. The Western Church can accept conciliarism+, or the Eastern Church can accept the absolute authority of Rome. There’s really no room for compromise here. Vatican-1 may have wiped out the last hope of reconciliation.
Big (but probably manageable) issues are the Western view of the Immaculate Conception and purgatory.