The IB is an all encompassing description for what is three different programs.

PYP for primary aged children.
MYP for middle school to IGCSE level.
IBDP for the diploma program, post 16 education.

I presume you are comparing MYP with IGCSE. I teach IGCSE and IBDP but I have never taught the MYP, but based on my experience of teaching students who have done both to enter the IBDP, it doesn't make much difference.

IGCSEs are more difficult than UK GCSEs so do not compare them to those.