Most of the POS system depends upon the back-office system. This means that if the back office PC fails so does the entire POS terminal. It also looks like a big limitation but most restaurants never fail.
Almost every restaurant is using its POS systems to credit card processing. They require internet access to connect the restaurant for their credit card processor. You can get magento pos through the internet.
Most of the PC requires an internet connection for the database. Fortunately, most point restaurant sale system can utilize the mobile phone backup connections from network routers to process the credit card when the restaurant lose their internet DSL connection.
PC-based restaurant POS systems have evolved and matured over the years to include the features and options designed specifically for the hospitality market.
The new tablet POS restaurant system does not waste time and spends heavily on development to catch up. So check out the tablet market when you are investigating a point of sale system to see what would be most suitable for a particular restaurant.
And when you do, make sure in your research you are comparing apples to apples and maintain all the benefits and features you want in either PC or tablet-based system.