I have been hearing that always the march exam sessions of f6 is little bit harder since that is the last time the finance act of that particular year is been tested. Is it true?
I do not know where you heard that from but it is impossible to say as we only see a sample paper for the March and June exams so we do not know the exact content of the March paper to make such a judgement. If you have been preparing for the March paper then sit it as the June exam will be based on FA 2017. If you have not yet started your studies then wait and prepare for the June exam