I think it doesn’t really matter what pre-IB course you take because the content remains fairly similar or even identical. With that being said, any programme would prepare you for the IB Diploma Programme (IBDP).
I did the Cambridge IGCSE before embarking on my IB journey, so there wasn’t too much of a difference regarding the content. However, it is definitely useful to have taken subjects you would continue to take in the IB (e.g. IGCSE Biology if you’re planning to study IB Biology or Maths and Additional Maths for IB Maths HL/SL).
For me, the biggest change when transitioning to the IBDP was having coursework. My IGCSE experience was very exam-based. Although you can submit coursework for subjects such as English literature and the sciences, most schools opt out. This means your all your IGCSE grades are based upon the final examinations in May/June or October/November.
That said, the MYP (Middle Years Programme) prepares you much better for the Internal Assessments, Theory of Knowledge, and Extended Essay components of the IBDP. If you’re diligent and hardworking, you shouldn’t really find it challenging because your teachers are there to guide you. And, you can always look up resources and sample work online!
On the other hand, IGCSE (or other programmes) would allow flexible subject combinations that help you explore your interests. I took English, Chinese, Maths, Biology, Chemistry, Business, and Sociology.
In sum, I’d say the MYP provides a more solid foundation for the IBDP – it’s more helpful for those who want to get used to the rigour of coursework. But remember, you can always explore your interests prior to doing the IBDP, so it’s up to you!