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As far as I know the powerhead method is more CO2 efficient - no CO2 bubbles go straight up and out of the tank but also adds to the electric bill. With a smaller tank the zigzag ladder is prabably ok. But if you have a large tank that needs lots of CO2 you need a powerhead.
If you're paying for a pressurized CO2 system, you should go with a more efficient reactor.
If you run a canister filter, you can put a reactor in-line on your return hose. about $10 to make one outta PVC.