do a FAA PPL - its-s quicker in the respect that when you sit your "check ride" - when you pass, you get your licence there and then. If you get a JAA PPL, you have to wait up to 60 days for the licence to be issued.
So if your looking to do hour building on the cheap, get a FAA PPL, then hour build in USA.
When you go onto to your JAA APLT, CPL, IR etc, it wont matter that you have a FAA PPL.
Does that help?