IB Psychology vs IB chemistryWatch
I think the main deciding factor should be what you want to study at university.
I am currently taking IB Chemistry HL. Chemistry HL is a tough course, and if it's between these 2 courses (at HL level) psychology would be the way to go. Chemistry SL, however, is way more doable than chemistry HL.
So if it's an SL course take Chemistry, but if it's an HL course take Psychology.