From these two PSUs, I would go for the OCZ's unit without any doubt.
The unit from Cooler Master presents a poor voltage regulation and the ripple/noise levels are too high at full loads. Moreover, it seems that the protections aren't working properly.
Both are made by the same amnufacturer: Sirtec. Unfortunately, there isn't any qualified review for the KMRK4-P-550A yet. Therefore, since the model from OCZ can deliver 50w more than the Scythe's unit, I would go for the OCZ at the same price.