As Gaz says, the 'Hammer' map seems to be putting out around the 310bhp mark which is about as good as you will get for Stage 1 on a ED30 anyway, whether it be GIAC or Revo. If you want to go for more power then that is where the Milltek TBE, EVOMS and pump etc come in. With GIAC and the following mods, the best I have seen/heard of for GIAC is around the 330bhp mark. Where as with the Stage 2+ available from Revo there are already quite a few Ed30/Cupra/S3's running 350-60bhp as the map has been developed to work along side the HPFP and get the best gains.
All depends on whether you want power figures or how you want the power delivered etc. But as RR has said, the customer service from Revo is excellent and with the Select + switch allows you to fine tune you settings to give the option of how you want you power delivered etc..
I don't think you will go wrong with either map mate to be honest. As customers from both stables seem to be chuffed to bits with their product and it is also very rare to hear of any problems arrising from either tuner..