Of sections 12, 13 and 14, which is best for a concert at Bankers Life Fieldhouse?

Section 12 has the Best Angle Towards the Stage

All three sections are about the same distance from the stage, so there's no real advantage to any of them from that perspective. But what we like about Section 12 vs. 13 and 14 is the angle towards the stage.

The seats in Sections 13 and 14 are angled towards the middle of the floor since this is primarily a basketball venue and that's where most of the action would occur. Thus, for a concert you have to turn your head to the left to get a good view of the stage. Meanwhile, Section 12 has a better angle towards the end-stage set-up with less strain on your neck.

Note: these comments assume an end-stage setup with the stage in front of lower level sections 1 and 20.