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I don't have an iPad Pro 12.9" but I have seen them in stores and I've had my MBP for a little over 24 hours. Based on that I'd say the MacBook Pro but that's a completely subjective assessment.
 
I have iPad Pro 12.9" and it is similar but has more off-angle brightness falloff than the MacBook Pro. Not surprising since it's a high-res digitizer as well.
 
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