I've studied in both mediums - CBSE from the 1st to the 8th and ICSE from then on. IMO, CBSE has a lot more theory while ICSE places a lot more emphasis on practical work. For some reason, Hindi under CBSE was frackin difficult to score while ICSE was pretty easy, possibly due to the slightly more lenient scoring system. However, the option to learn French in the CBSE system was a vital plus while Accounts under ICSE was quite boring to be honest. The fact that ICSE is slightly easier is evidenced by my annual % graph - I went down to 80% in the 8th grade but shot back up to 95% in ICSE.