The instant reinforcements (ODST Drop) and the orbital PWN cannon allows Cutter to stop any gaps in his line rather swiftly. Carpet Bomb and Cryo just don't get the job done like the MAC.
Cov sucks at turtles due to the fact that their anti-vehicle SUCKS compared to the Cobra when placed on defense.
EDIT: Though I could make a strong case for the Arbiter.
Christian, Conservative, Republican. In that Order. -Mike Pence, Indiana Congressman
Death to the WaffenSS!
You just can't fix stupid.