Sorry
you are both absolutely correct, my apologies.
ARA's are flown on the rad alt, primarily, unless broken of course.
when i say set BARO to rad alt, this is done to avoid confusion when looking at different altimeters. your standby alt is still set to QNH.
in the aircraft i fly the BARO is on the PFD and the rad alt is on the NMD, so its easier to align the two so that the PFD becomes your primary instrument.