At least when using QNH you know your height in relation to the the MSA, no mental gymnastics required. In the company I work for, we only set the DH on the rad alt when carrying out a CAT2 or CAT3 approach, because outside of these parameters, 100/50', the rad alt is not reliable because the terrain is not constantly level! You do get used to making all decisions with regard to altitude using airfields as diverse Amsterdam and Munich. It must only be the military that do not have a means of setting the pressure setting in inches or Mb on their altimeters. But then what do I know!