Are you asking for Liturgical or Theological differences?I suppose both. I am sure the bulk of the theology is the same, but someone mentioned a couple slight differences between Coptic and Armenian such as whose baptism was accepted, etc. There were some interesting comments on how worship is conducts and customs and on what is Tesbeha in the Coptic Church that is not in the Armenian. I am looking for stuff like that. Is there anything I should know if I visit?
Er, all of our Theology is the same (at least it should be). As I understood it, the difference between which baptisms are accepted have more to do with the application of Economy.
Back on topic, I think you'll find Syriac practice much more similar to Armenian practice when compared to Coptic rite. E.G, Deacons being allowed to cense, communion being given under two kinds simultaneously, etc. I think this is due to the more frequent contact between the Armenian and Syrian churches through the centuries.