Saint AAI

Im looking at engine management at the mo and was wondering what peoples thoughts on both these units are, pros and cons etc... I know the GReddy is a piggyback and the Apexi is stand alone, but what else is there to consider. I want to have ago at the mapping myself, so need to know which is easiest to get to grips with. I know the E-manage allows you to play about with the existing map and switch between different ones, which sounds good to me as if something goes wrong I can switch back to standard map. Also I know the Apex comes with a pre done map which allows you to start and run the car initially, but how good is this map over standard?? And my last question is that I have a Zero/Sports ECU so will the GReddy be able to plug into this as it looks like the Zero/Sports is just a re-mapped standard ECU to me??? Comments please.