Cbse isn't tough. But nbse is easier than cbse as cbse has more detailed studies compared to nbse. So in brief : nbse is easier than cbse. (I came from nbse(8years) to cbse(4 years) )

hope it helped.

CBSE is compared to be more difficult. It is a common board followed by many schools throughtout the country that's why it's significance is more than the local boards. In terms of standards also cbse keeps updating the curriculum