Your teacher is the best person to help you decide this, since he or she is familiar with your abilities and what would show you off to your best advantage. If you are about to take this examination, I assume you have already learned your pieces. Are you trying to decide in which order to play them? We can’t help you here without knowing what you’re playing.
I never took ATCL exams, but I did take RCM exams in piano. The ATCL syllabus should have explanations about how their examinations are run and whether you or the examiners chooses the order of the programme.