What I would say (as someone who spent most of his life as a RC, became Orthodox 3 years ago) is that on an initial look, from either the
Protestant or RC perspective, Orthodoxy can look a lot like Roman Catholicism. We Orthodox have an ordained priesthood, sacraments, primacy of the Eucharist, Bishops, ornate vestments and ritual, and the like. Externally we can seem like an exotic form of Roman Catholicism. But it's when you get to see things closer up that they begin to look different. How we conceive of all of these things, what they mean in our spiritual lives, is very different than in Roman Catholicism. It's very hard to understand this, however, at first glance --- it takes a bit more experience with Orthodoxy, I think