You should do geography because you'll get a higher grade on it and you enjoy it. Unless you need computing science GCSE for a level computing science, which some sixth form/colleges do, and that a level computing science is needed for a degree that links with that but idk so you should do research. Honestly, you don't need a specific GCSEs subject you need to do, just good enough grades like 9-4 unless you need it for competitiveness for a uni degree which is competitive. It only matters for education after secondary and before uni.