RPS is more conservative.
Sure, in the sense of fairly uselessly adding 1000ft to everything, on some days
It will not give you pressure altitude, which you need for quadrantial/semicircular rule, it will not give you separation from controlled airspace,
If a GPS delivers true altitude, then it's good for CAS separation where CAS is defined as altitude.
Obviously I agree re the other reasons for
barometric altimetry... I was just being provocative
I posted
this a while ago. That is an old GPS, without EGNOS. For some reason I didn't include the yoke-mounted Garmin 496 which uses EGNOS and is super accurate in altitude.