I can’t tell you if there is any duplication of records as I don’t use the English version, but there are some records on the FindMyPast.ie version that are unique to Ireland eg prison and court records, and Encumbered Estates Records. It doesn’t have the Irish censuses but that is presumably because they are available free elsewhere. It does have some census substitute sources (which compensate for the destruction of the Irish censuses pre 1901). It doesn’t have the statutory BMDs but it does have some early marriage bonds and info like that. Also various census substitute sources, migration records, some military records, newspapers & directories. So you will see some different material on it.