They are not really different types of power supply, they are specifications. ATX12V 1.0 was an extention to ATX 2.03 which increased 12V output and changed a few other things. All new PSUs should meet both specifiacations, so don't worry about that. Just get the one with the right plugs (20 or 24 pin depending on motherboard, etc) and make sure it's a good brand.