Just a simple reply from my side.
CX400 is just better.
--> Higher Efficiency, means less power loss, means less heat production, means more lifetime of the product
--> Can provide upto 472W on Full 3d Load while keeping the efficiency above 80%. They tried pulling even more but that dropped the efficiency below 80%, 79% to be exact.
--> Having 30 amps on 12v rail, which means Guarantee of running a GTX260, HD4870, GTX275 and still with a Overclocked Dual Core, and a Normally Overclocked Quad Core.
While the Cooler Master has 70% "Typical" efficiency, which drops below 70% when you try to pull more from it. And apart from all that, those suckers didn't even mention the Power Draw on 12v rail.
From various resources, it is confirmed that CM600 is just a rebranded CM500W.