Also, I think it's not just the actual transaction time, those handhelds probably make the connection/login with each transaction. Like in the early days when smaller business had POS cc/debit card machine -- they would swipe the card, you would hear the modem connecting, then a few seconds while it authenticated, then the transaction would run, etc.. That process might add some more time to each transaction.

Might not seem like much, but when the FA is working there way down the aisle trying to get to everybody, it could add up.