The only real reason for the CPL theory is to become a flight instructor that doesn’t anticipate gaining an IR within 3 years of passing the exams.
There is about 1/3 content removed from the CPL theory (no global climatology, no NATS, no turbine powerplant etc. etc.) so they are a little easier and the candidate is subjected to a little less time pressure as the exams are fewer and generally contain less questions.