Are one of these preferred for food/transportation charges? I don't have either yet and only want to use one while abroad. Recommendations?
They are basically the same thing, as I understand it - they allow you to pay with your credit/debit card by tapping your phone.
In many markets, Google Pay has been withdrawn and replaced with Google Wallet. You don't necessarily need either app - you can just tap your contactless card, which is what I do. If your card is for some reason not contactless, then tapping you phone is a good option, though.
I'm in the UK at the moment, and just use my credit card for tube/bus and payments.
I use Google Pay 99% of the time in the UK. And I spend a lot of time in the UK. I've spent three of the last four months here including now.