I have tried many MC and MM cartridges with my Croft 25R+ and without doubt the 2M Black is the best performing cartridge by far. It was way better than most MC cartridges I have tried.

The Decca Blue cartridge was also no match to the 2M in almost every respect. The high output of the 2M and its vivid "live" sound are truly outstanding with the Croft 25R+ ( This is similar to the RS as it has the same line stage). I know the RIAA RS though has the separate PSU and better phono stage implementation so may sound even better with a 2M Black. Even the live immediate sound of the Decca cannot match the 2M Blacks stunning dynamics and delivery.

If you do decide to go the 2M Black route maybe try and get a used cartridge and have a Fritz Gyger S stylus fitted by Holistic Audio in Holland. This will give you a very special cartridge indeed which would be very difficult to better with any MC never mind MM cartridge. I am recommending this as a Croft user and from my own personal experience.