There is no practical difference between the IMCR and the IR, a few years down the road, within the limits of their respective privileges.
It all comes down to currency on type, currency on type, currency on type, and whether the man has the fund$ to get his hands on a decent plane. And you are only ever as good as your last flight.
The two training products are aimed at different markets and this is what results in one having often ropey currency - lack of time/money to fly and lack of access to a decent IFR plane.
Whereas somebody with an IR will either be using it on their own substantial flying budget, will be getting someone else to pay for it all, or will let it lapse.
Almost nobody will do an IR to fly rented spamcans. Most are illegal for IFR in CAS anyway.
Incidentally
20hrs/year instrument flight is plenty and is far more than the vast majority of IRs get. Most IFR flight is in VMC anyway, and most is on autopilot. If I was flying 500hrs/year (which is at the limit of what is possible while having any kind of life) and all of it on airways flights, I would not be logging as much as 20hrs/year instrument flight. Not HONESTLY.
The more clever you are in the weather/route planning, and/or the more powerful plane you fly, the less instrument time you will log.
Hilariously, the pilots who log the most instrument time are
a) pilots of unpressurised public transports (Trilanders and such) who fly at ~ FL100 max, and in bad weather they either fly in IMC (plenty of sick bags get used then) or they scud run the knackered old dogs over the sea at 700ft, all nice cosy CAA authorised stuff which is exactly what private IFR pilots try damn hard to avoid doing by flying VMC on top on oxygen in sunshine
b) pilots of > 1999kg piston twins who fly "VFR"
to avoid IFR charges - one often can't get to VMC on top while VFR because one can't get the clearance into CAS, so this kind of flying is often sitting in the muck the whole way
Pot and kettle come to mind when I read ostensibly professional pilots knocking somebody here.