Almost every "best restaurant POS" list is written for a building. A building has wifi, a power socket behind the till, and a router somebody else maintains. You have a 4G dongle, an inverter, and a lunch rush that starts the moment three office blocks empty out.
That changes the ranking completely. Offline behaviour stops being a footnote and becomes the first thing to check, and the way each system handles a dropped connection differs more than the marketing suggests. Square will take the card while offline but cannot confirm it will clear, so a declined payment shows up later, after the customer has walked off with their food. TouchBistro keeps running properly because the iPads talk to each other over a local network rather than to a data centre, which is architecturally the right answer, though it costs more and expects an annual contract. Toast holds up well on its own hardware but that hardware is the entire point of Toast, and it is not coming out of a service window at the end of the night without a plan.
The second thing that changes is what "cheap" means. Subscription price is the number vendors compete on, and it is the smaller number. At truck ticket sizes, the card processing rate is where the money actually goes: on $120,000 a year of card sales, the gap between 2.49% and 2.99% is around $600, which is most of a year of subscription on any plan here. So when you compare, add the two together or you will pick the wrong one.