Need help on PSU 12V amp

I need to know how to choose a right power supply.
The question is about the amps on the 12V rails. Lets say two psu has similar output power, where
PSU1: Having more than 12V rails rated with 15A
PSU2: Having two 12V rails rated with 18A

So, how can I know which one is better? Thanks

I need to know how to choose a right power supply.
The question is about the amps on the 12V rails. Lets say two psu has similar output power, where
PSU1: Having more than 12V rails rated with 15A
PSU2: Having two 12V rails rated with 18A

So, how can I know which one is better? Thanks

MRXwee

If both have the same maximum output from their respective 12V rails when they are all at use (NOT just by adding them though; there should be a value in watts given to you on the 12V total output), I would personally go with the one that has the least amount of rails. The reason is that by doing so, the risk of you overloading a 12V rail is lower due to more of the cumulative output being available on that one rails compared to one from a PSU with more 12V rails to distribute the power to.

So meaning that Less Rail + high amps will be a better choice then.
Before I just wondering that would 15/16A on the 12V rails is enough to run gpu like GTX560 - GTX580 or HD6950/HD6970 compare to amps of 18A or higher.