Actually, you have no idea how much power the cooler master has on the 12V rails, it doesnt give you their combined rating. Almost never will two 12V rails with 18A max on each add up to 36A between the two, they are pulled from a common 12V source. I suspect that the Cooler Master will only give you about 34A on the 12V rail which is weak for a 600W unit. It also has passive PFC which is a sign of an older less efficient design, and isnt 80+ certified so its less efficient than the corsair and is not necessarily guaranteed to run at 100% load.
I too would go with the corsair.