Yeah, I mean, they were totally identical. One of them was a wry existentialist, while the other was a total zealot. One of them quietly stalked the crew before sneaking on board, unseen, and methodically disabling each one of them, and the other devastated like a dozen planets in order to flush Mal out like a rabbit. One was getting to River through Mal, and the other was getting to her through Simon. One carried a slug-thrower, and the other had a laser pistol. One was a short haired black guy, and the other was a short-haired black guy.
Okay, maybe there was only the one thing they had in common.