Hello Sankalan
Chemical engineering and Instrumentation engineering are two completely different fields so you can not really compare them with each other.
If you like chemistry, either organic and inorganic and don't want to study maths much, then you can opt for chemical engineering as it deals with mostly lab oriented reactions and mechanisms.
However, if you like electronics and mechanical portion then you can instrumentation engineering, which is a new branch in india and still developing.
Hope this has answered your query.