The answer to that question lies with the student and what suits them. Both will get you into any university in the UK or around the World. The difference is in the number of subjects and the depth at which each is studied. With A levels, 3 or 4 subjects are studied intensively. (students doing Further Maths or who want to study Medicine do 4 usually). The subjects chosen are often related to the degree programme they wish to follow. IB Diploma students choose six subjects in compulsory core areas which are Language & Literature, Language Acquisition, Sciences, Maths, Social Sciences, and the Arts.