I personally found the cpl more subjective than the IR. IR is all black and white, follow that heading, fly the hold, etc. it is as per the plate which takes some thought and judement out of it somewhat.
Cpl is about you making the correct safe, commercial calls, vfr navigation etc.
Both have there trickier aspects, on balance IR i found tougher, as your learning new skills, cpl is about polishing existing skills