I am qualified to answer this because I opted for ISC in class 12th.
DO NOT opt for ISC at any cost if you are serious about your JEE or NEET.
The syllabus in PCM is exactly same as CBSE but English is a real pain.As I passed out of ICSE I thought english wont be that hard but I was completely wrong. I wanted to switch my board just after 6 months but it felt too late. My other friends have had a similar experience. All of us regretted our decision to continue with this disastrous board.
Do not, do not, do not assume that English is same level as that of ICSE. It just gets worse, too much quotations, rote learning, etc when the student has to focus on Science. I myself didn't get any time for it and I had to literally waste my last two months before the boards studying it. .
And guess what, the board papers of PCM are also of same level as that of CBSE. While in cbse students easily get 90 or 92+ in English in ISC it's a dream to even touch 90. So you will get lower percentages in boards than your CBSE friends with same/ extra hard work.
I have made this mistake, you don't. Good luck.
sdfg 63 days ago