Henson has one decent season in college and all of a sudden he's going to be the savior in Big D? That's just what Dallas needed, another inexperienced QB who hasn't been around the game of football for a few years. In case you haven't guessed, I wasn't very excited about the prospect of Hneson playing for the Pack.
So yeah, I'd much rather take Couch over Henson.
Couch, on the other hand, hasn't been as successful as you'd hope for #1 overall draft pick but he does have experience and has shown flashes of being a pretty good NFL QB. Also, look at his OL and supporting cast at the skill positions and the offensive gameplan for the Browns. They don't exactly strike fear in DC's eyes around the league.
How long is it going to take Henson to adjust to the mental part of being an NFL QB? The learning curve suggests a few years. Couch's struggles with the Browns go a lot deeper than his abilities as I alluded to earlier..