It sounds like Barrett has a ways to go, which is fine. Barrett is the type of QB who takes more time to mature:
Herman said. "I tell J.T., 'You get paid (a scholarship) to make good decisions, get the ball out of your hand and be accurate. You're not gonna grow. Your arm this year is not going to get a whole lot stronger, at least not this year. Be on time, be accurate and be right with what you do with the football.'"
Chase Daniel redshirted, then threw for 347 yds, 1 TD, 2 INTs in mop up time as a redshirt frosh. He played well as a sophomore, but steadily improved every season. By his junior and senior seasons, he was the epitome what Herman is describing above.
In contrast, Cardale has the body and arm to make an immediate impact on offense:
Herman: "Cardale is 6-5 and 250 pounds and can throw it through that wall. 'Use some of that. Use the talents that you have while we develop the portions of your game that need to be developed.'"
Cardale can play a Tebow-esque role, i.e. the QB as battering ram FB in the read option, which would be a good complement to the likes of D Wilson, Samuel, Marshall, etc. Heck, it wouldn't surprise me if Urbz rotates Cardale in for Braxton for a few plays per game just to throw a wrinkle at defenses and help limit Braxton's carries.
In other words, Cardale can help without necessarily having a full-grasp of the offense and/or throwing accuracy, while Barrett can help only after he has developed those qualities; hence, we'd expect Cardale to be ahead on the depth chart. If, by the fall, we're hearing that Barrett is challenging for the #2 spot, that'll be a sign that Barrett is halfway to becoming a witch, which would be very good news.