ChiChiPaPa asked a very good question, which I asked myself 2 years ago. I searched in the internet to find any researches or expert reports to compare the two exams, but I can't find any IB vs HKDSE (more IB vs AP and IB vs GCE AL).
I used a stupid method to compare the two exam. I use indirect comparison method from UCAS's expert reports, IB vs GCE AL and HKDSE vs GCE AL as reference.
Moreover, I researched the university admission requirement and credit recognition as reference as well.
1. May be some parents aware, the IBers of this year still can take 3-year programs in HK, but HKDSE only go for 4-year programs. From next year onward, IBer can have credit recognition of HL subjects in HK, UK and US....... but not for HKDSE.
2. From my observation HKAL > IB/AP > HKDSE > HKCEE > GCSE
3. It's not a scientific comparison, I used IB score 6/7 vs HKDSE 5*/5**
IB HKDSE
Chinese A HL >
Chinese A SL >/=
English A HL >
English A SL <
Maths HL M1 < Maths HL =/< M2
Maths SL = M1
Chemistry HL >
Chemistry SL <
Economics HL >
Economics SL <
TOK/EE >> LS
CAS > OLE
Just for reference, other parents can share their views.........