2 things:
First, timing matters. Go over the combat logs and you may see that DP machamp dies at 25 energy, losing efficiency, whereas CC machamp lands his CC right before he dies.
Second, in a pure dps race DP wins. Also in raids a 50E move allows you to be a little conservative on when you dodge and attack without wasting DPS.
I ran the simulation of machamp vs magikarp as a raid 5 boss. It shows DP outperforming CC.
https://www.pokebattler.com/fights/attackers/MACHAMP/quickMoves/COUNTER_FAST/cinMoves/DYNAMIC_PUNCH/levels/30/ivs/FFF/defenders/MAGIKARP/quickMoves/SPLASH_FAST/cinMoves/STRUGGLE/levels/50/ivs/001E13/strategies/CINEMATIC_ATTACK_WHEN_POSSIBLE/DEFENSE_RANDOM_MC?includeDetails=true&dodgeStrategy=DODGE_100&seed=1501252062652
https://www.pokebattler.com/fights/attackers/MACHAMP/quickMoves/COUNTER_FAST/cinMoves/CLOSE_COMBAT/levels/30/ivs/FFF/defenders/MAGIKARP/quickMoves/SPLASH_FAST/cinMoves/STRUGGLE/levels/50/ivs/001E13/strategies/CINEMATIC_ATTACK_WHEN_POSSIBLE/DEFENSE_RANDOM_MC?includeDetails=true&seed=1501252069438
