It's also pretty easy to take an item and walk out without paying. But it doesn't happen. At least, it doesn't happen that much, and I would guess it happens much less in China than in the USA (though I'd be curious to see actual shrinkage numbers).
QR codes seem to have largely supplanted cash and credit cards in mainland China, whatever hypothetical downsides they might have. And the very limited hypothetical advantages of NFC (it's unclear to me what they actually are, but let's grant they exist) don't compensate for the fact that an expensive terminal is needed, so NFC isn't displacing QR codes in the near future.
It doesn't have a bearing on which method is riskier, but it does have a bearing on the idea that everyone is going to be generating fake receipts on their phones.
And, yeah, most places do verify based on another phone.
QR codes seem to have largely supplanted cash and credit cards in mainland China, whatever hypothetical downsides they might have. And the very limited hypothetical advantages of NFC (it's unclear to me what they actually are, but let's grant they exist) don't compensate for the fact that an expensive terminal is needed, so NFC isn't displacing QR codes in the near future.