Not controversial at all that one. Thinnest of edges and an audible snick.
What's proven the decisive factor was the way that each team used the referral system. Clarke wasted reviews and ended up not being able to do anything about Broad, but Cook played it sensibly and ended up being able to overturn Haddin's non-dismissal.
It'll be interesting to see Clarke's approach towards DRS going forward. Seems that he didn't learn anything from the Broad situation given that he threw a referral away on trying to get his own dismissal overturned in the second innings.