Most of your industrial automation applications probably have a need for both real-time control and operator interface. If you're using two separate components to make this happen, you can save money and time by instead using just one, a combined PC-based controller and graphical operator interface.
Money is saved because the combined unit will be less expensive then separate components. Space is also saved, as is implementation time, as there's no need to integrate the controller with the operator interface.
If you decide a combined unit is a better choice, look to Advantech line of Panels PCs to address your specific needs. You'll find a wide range of solutions capable of addressing very complex applications on the high-end and handling simpler applications in a cost-effective manner on the low-end.