Neither A or B because I'm not rich and have to choose carefully when making a purchase so things like Color don't matter.
C. The thing I would be looking for most would be to make sure it had all the connections I would need for my machine. The second thing I would look for would be reliability since a power supply isn't something I want to be forced to repurchase for a long time.
It appears that either of the power supplies you asked about have both of those qualities.