underfire:
For the discussion, both criteria considers RNP to be non-precision.
The FAA considers RNP AR, LPV, and LNAV/VNAV to be neither precision, nor NPAs. The current party line is that they are approaches with vertical guidance (APVs).
VEB and GQS are good concepts, but need to be developed further.
Quite separate concepts. In the US the GQS applies to all APVs, as well as ILS and GLS.
With either criteria, with RNP, VEB, you have a minimum of a 200' obstacle clearance with a 50 foot minimum momentary descent, hence it will never get below the 250' min.
The FAA has a different take on it. Because it is barometric VNAV, it has non-precision required obstacle clearance (ROC), which is the same for NPAs and Baro VNAV. The maximum possible height loss at DA in FAA RNP AR is accounted for in the transition to missed approach criteria.
The procedure design by third parties is usually very platform specific. The FMC combinations can act differently, even between same aircraft with different airlines, depending on the configuration. Obstacles must be independently mapped and verified.
That can be true for specials but third party developers in the U.S., of which there are two, must develop to public RNP AR criteria. They cannot account for OEI, unlike in some other countries.
The FAA and regulators require significant amount of money be spent to certify and validate the procedure for use, and there is ongoing maintenance of the procedures for every cycle.
So much so most of business aviation avoids getting involved, even with fully compliant airframes.
Third party developers include also EO, weight limit, and DEP procedures, which are not defined in the criteria.
Again, not so for public RNP AR procedures in the U.S.
All of this costs a lot of money...
No doubt about that!