What is the difference between the two available POS devices?

A920 - The A920 combines the full features of an Android phone with a powerful payment terminal, all in a sleek and compact design. It has an integrated camera, a printer, and a high-capacity battery to meet the daily demands of your retail business.

D180 - The D180 is a stylish and cost-effective wireless m-POS terminal, which connects to a wide range of smartphones, tablets, and PCs. It is easy to use, convenient and delivers a seamless transaction experience.