I got Audio and Notes for BEC in order to get a jump start while traveling. There is a good amount of overlap between the two so it depends on the learner (auditory or visual or a little of both). The Notes have a bit more info on specific formulas, etc. Best bet is to get the free sample that is provided and compare.
I haven't used them to follow along with each other but to use one when I can't use the other. Both are meant for repeat reading/listening. Commute, workout – audio. Reinforcing difficult content or bringing together sections – notes.
AUD - 77 BEC - 81 FAR - 77 REG - 81
REG - 1. Becker only - fail (forgot to study depr - oops); 2. Becker only - Pass
FAR - 1. Becker only - fail; 2. added Ninja Notes and MCQ - Pass
AUD - 1. Becker videos; Ninja Notes, Audio, MCQ, Becker Notes - Pass
BEC - 1. Ninja Notes, Audio, MCQ, Becker Notes - Pass