I'd say Audio.
It's better to put things in your own words. You tend to remember and see the material better than just reading someone else's.
A good start is the act of transcribing the audio. Plus, you can take it with you to listen during an idle moment while in the car, at the gym, etc.
They can serve as a bedrock for your own notes as you progress with the multiple choice practice. You'd add to them any solutions to MCQs you found difficult or presented the material better. Again, the act of putting things in your own words helps memorizing.
The NINJA notes aren't without merit. I'd say get both if you can. The Notes are good to help clarify a solution you may not understand.
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Then again, everyone is different. That's what I did for each section, more or less.
Best of luck!
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