One thing about NFC is that it does not require an active data connection, whereas Square does. That may not seem important, but for those of us who live in the middle of nowhere, it's relevant. I'm not sure that it's relevant enough to change wide-scale adoption patterns, but in my small town, there are multiple locations in CDMA black-holes that are PayPass enabled, thus accept Google Wallet. Every single Mobile station, and nearly every other big-chain gas station is already set up for NFC.

According to the Square App, I have to drive 11 miles away to find the nearest accepted location.

Ultimately, I think both will operate in parallel for quite some time until Apple decides to release something and takes over the world of payments overnight. :)