PC-based
A PC (personal computer) control system utilises a computer for information processing and control, often in the form of a panel PC – a touch screen and PC built together. Process signals are generally wired to remote I/O racks which communicate with the PC over an Ethernet or serial interface.
PLC-based
PLC control systems use a dedicated logic controller designed for industrial control. Process signals can be wired to I/O modules directly connected to the PLC, or over remote I/O racks via Ethernet or serial.
Which type is best for my system?
PC control systems tend to be more flexible and powerful than a PLC system, and are particularly effective when interfacing with existing PC-based infrastructure such as databases and company ERP systems. However, for small to medium systems, a PLC-based system will be much cheaper and simpler than a PC, and will be more reliable in harsh environments or temperatures.