Here is the current compatibility list for Square:
https://squareup.com/help/en-us/article/3887-device-compatibility-with-squareI havent used the PayPal option, so Im not sure if they offer the same type of network, but with Square, my customers and I are afforded the ease of having their information already stored (if they are previous Square users), so I dont always have to ask and type in full email addresses or phone numbers to email or text their receipt.
I do feel that Square is more popular in my area than the PayPal version, so as a vendor, it behooves me to use the service that more of my buyers are familiar and associated with, but PayPal could be the way to go for someone else!
(I think the price difference is PayPal: 2.7% vs Square: 2.75%)