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.
but the cooler master has more power on the +12v rail, although its on a dual +12v rail.
actually they both have just about the same amount of amps on their 12v but the corsair can deliver over 500w (even though it labeled 450w) of continuous power with ease. I highly doubt the CM can do that even though its labeled 600w. CM is notorious for over rating their PSU.
corsair review You will bring home a relatively inexpensive power supply that even though is sold as being a 450 W unit can deliver up to 570 W at 48º C – in fact Corsair could have easily labeled this power supply as a 500 W unit, but they preferred to stay on the safe side.