4 A levels and WBQ

I’m a year 11 student currently studying in Wales. I’m thinking of doing 4 A levels + the Welsh Baccalaureate Skills Challenge (which is kind of like an EPQ, but worth a full a level) in sixth form, and i’m wondering if it’s worth it. I want to take:

-Biology
-Chemisty
-Maths
and either
-History or
-Psychology

In my school, you have to do welsh bacc and it’s accepted by many jobs as a full A level in many universities (except for oxbridge!), and is used in many conditional offers if you do not achieve desired grades in a certain subject, WBQ can be used to bolster your grades. Universities, even Oxbridge, value it as it involves using many skills. I’m planning on studying medicine, and I am considering applying to Cambridge.

I’m currently taking these GCSEs:

- English Language
- English Literature
- French
- Biology (Triple)
- Chemistry (Triple)
- Physics (Triple)
- Mathematics
- Numeracy
- L2 Further Mathematics
- Business Studies
- History
- Religious Studies
- Welsh (second language)
- Welsh Baccalaureate 

I have already achieved or am predicted A*s in all my subjects, and i have done volunteering for over 3 years, and have achieved birth my DoFE bronze and silver, and am planning on doing my gold.

I wanted to know if I should do History or Psychology for my 4th A level in order to apply for medicine, both are equally interesting to me and I have to do a 4th AS level throughout year 12 at my school. I was wondering if doing continuing this until year 13 and getting a 4th A level will make me more competitive to apply for medicine, and for oxbridge specifically.

Thank you!