You are a "Rockwell shop." If your HMI/SCADA is FactoryTalk and you want to streamline your licensing and support through a single vendor, Enterprise is the way to go.
While they share a common DNA, the choice between them usually comes down to your software ecosystem—specifically whether you are a dedicated Rockwell Automation user or a platform-agnostic integrator. What is KEPServerEX? kepserver enterprise vs kepserverex
Based on benchmark tests from Kepware user groups and internal PTC documentation: You are a "Rockwell shop