If you want to discuss these types of matters, please seek advice on the RD Forum, where you find my views reflect the experience of many many others in NZ AU, US and elsewhere. The US firmware works perfectly well in New Zealand. The US R3 firmware in particular is superior than the NZA firmware, many NZA R3s have been converted over now. I offer both firmware versions on the R3 but recommend the US firmware for the R3 in NZ as it covers the same range, frequencies and sensitivity, but with better support and functionality.
The R3 and R7 KA band frequency ranges both extend beyond what is required in NZ. This why you would be advised to cut the range down in NZ to Ka band segmentation 4, 5, and 6 for the NZ police frequencies. The R7 has K band scanning range that extends below the frequency needed for the NZ mobile redflex regardless of firmware. Therefore the R7 is superior to the R3 regardless what firmware you install. Hope that helps.
Myself and others have actually tested the R3 in NZ comparing both the US and NZA firmware installed on the same actual unit. The range is the same, and typically slightly better than the original escort redline.