In both PCMC and PCME, the common subjects are Physics, Chemistry and Mathematics and the only difference is whether you should opt for Computers or Electronics as a fourth option. The choice depends on your interest towards the subject. I feel in Physics, you will cover some part of the Electronics subject and hence if you join any Electronics related branches at degree level, you won't face much difficulty even if you don't take PCME. Personally, I would recommend you to join PCMC because it will be advantageous if you join Computer Science related branches and even if you join Electronics related branches, you will have some knowledge about computers because of PCMC at +2 level. You need to understand that an Electronics guy sometimes need to learn Computers but a Computers guy may or may not need to learn Electronics.