IMCr v IR
As whopity has already argued, it is irrelevant to compare the IMCr with the IR. Does the training and testing regimes do the job for what is required, is the real question.
Clearly the IMCr training and testing is fit for THE PURPOSE. The accident record, pilot error or not, is excellent with only one recorded fatality in 40 years. The support of the rating given by BALPA and the Guild of Air Traffic Controllers and of course the CAA are also proof that the IMCr pilot performs well when within controlled airspace.
All things can be improved and brought up to date. The IMC course is not exempt but otherwise proves its case easily. Only European chauvinism seeks to oppose it.