Personally I would say the Uk by the time you have added all the costs up for flights there visa's etc and food accomodation blah blah, then I would say find a good club to fly from in the UK for the PPL, I heard loads of storys of the FAA licence being a tad shabby! (expect angry American abuse here!) but people generally get there PPl there and then have to spend another 10 hours learning to fly properly, this is all I heard so dont take it as true but something to think about and although the weather is crap sometimes im sure you can drill through the PPL over the summer?
I came to NZ for mine as it had a good reputation for training and also the weather was brilliant, before it changed to winter now that is, I knew it would be more expensive coming here than the Uk but the weather was good everyday and its been good to see somwhere new. So no regrets, if you are doing it just to get the licence then I would stick with UK but if you can afford a long holiday then have a look elsewhere!