We have looked into both. aerothermal is attractive because no collector area is required. However the further we researched into it the further we lost interest in it. Even when talking to suppliers of both aerothermal & geothermal heat pumps - they recommend a geothermal pump over a aerothermal and its no sales pitch. They both cost roughly the same. Except with geothermal you have to have a vertical or horizontal collector.
On the positive side - the irish climate is supposed to be very suitable for the aerothermal heat pump
Hey AJL - hope you are keeping well and the house is going well. Not long now before your moving in!