the technologies have overlap in many use cases but are complementary, QR Codes need to be visible and NFC (as the "Near" implies) requires a receiver to be near; you also need to program an RFID chip to do NFC, for QR Codes all you need is a printer or a screen, again very different use cases from the publisher standpoint as well; I guess Google's choice has more to do with what they want Google places to turn in to that with a choice of technology by itself