The syllabus of CBSE board is more skill-based which stresses skill development and not theory-based. CBSE is credited with conducting national level exams like IIT and Medical entrance exams which are based on NCERT books in India.
The courses so offered in ICSE are far more advanced and more detailed as compared to that of CBSE. The major issue in the CBSE board in the textbooks and materials in is outdated. The students are not exposed to the latest information. So I would suggest going with the ICSE syllabus. For more information on the CBSE and ICSE read the article.