Even though, Roman Catholicism and Eastern Orthodoxy are very similar they held a few differences like their beliefs of the original sin, the language held in the services, or status in the church. These two religions are very similar, but they have a huge difference among themselves; the Pope.
Catholics believe in the Pope, the selected one who will give the word to the Catholic church. The one who will overrule any other lower-ranked member of the church. The Orthodox church has the "highest bishop", he is considered the first among equals, we could say he is the Orthodox Pope although, the highest bishop does not overrule other churches.
In conclusion, a valid distinction between Catholicism and Orthodox is the highest raked member of the church, rather Pope or Highest Bishop.