Hello Hashmi,
What is best for you can be decided only by you. What others can do is only guide you. The rest is in your hands.
For knowing the difference in their Scope(click).
If you consider time, CS can be completed faster.
If you consider exams, ICAI has always maintained their exam standard and ICSI has recently increased their standard and they both have become equally tough now.
Whether CA or CS, keep things in mind:
1. They both are professional courses and people value them highly.
2. You should try doing your articles in a top or large firms(if possible). This gives you a benefit after final. BUT this is not always true as many students have proved from time to time.
3. You should be patient in completing them. Neve back down just because you could not clear an attempt. Be patient, focus, plan and implement.
All the best with your career.
Regards,
Subhash.