Between Brown and Beasley neither are going to win a physical battle and get wide open. That's why having a guy like Diggs will open up the offense a ton.
Brown wins on speed and Beasley on quickness but neither is going to beat solid man coverage consistently because they aren't strong enough. Brown's route vs Peters against Baltimore at the end of the game is a good example. They aren't physical enough to get leverage on DBs. That's a drag on completion percentage.