Mac's, IB, AP and some enhanced programs always choose advanced level courses. That's why those programs always were considered better than the regular program. But for IB program, a student with a raw mark of 6 in the IB exam can be marked up to 100 in some schools while another student in other school with IB raw mark of 7 be marked 98 only. You can understand now universities need an adjustment factor for the students from different schools.