AA 25, 26, 27 would get you into most schools with a good GPA, with a high GPA including a high Science GPA you would be looking at Ivy League, including Harvard. To answer your question, IMO, a 27 is higher than a 25 and if you are trying to get into a school with limited seats and very competitive, every little bit counts.
Hope this helps
Nancy, co/owner, DAT Destroyer, Orgoman