I think both IB and A levels are both very good Pre-u courses that are internationally recognized and provide training (albeit in different ways). I believe that IB is the better course.However, I personally would pick A-levels.

This is because I think A levels is more suited towards the type of student that prefers 100% assessment by one exam (me ) and also more 'booksmart' in the sense that all we have to do is read the syllabus with less hands-on skill compared with IB holders who are all rounders as IB trains them to present things well, to think and analyse a situation properly etc.

Sorta depends on what kind of person you are, IMO.