I am not sure how good any of them works....
As for the different between Action Replay and Codebreaker...well they are two different companies for one. If however you do end up finding codes they will be neither Codebreaker or Action Replay, they will merely be codes which would then require further processing/encrypting to be turned into Codebreaker or Action Replay codes...something only the guys that that actually work there and some other expert code hackers know how to do though.