I speak as a holder of the IR(R) on a PPL with no ambitions to go further
IR(R) is UK only, more conservative minima and no Instrument Departures
It’s a shorter training requirement, it permits you to fly in IMC, the training makes you a better pilot, obviously trains and allows you to make instrument approaches and (speaking personally) will keep you alive
i’m sure someone more qualified than me will confirm whether or not the hours count towards a full IR