largely two different use cases, the question is what type of 'network' are you working with?
:: connected linear features, roads, rivers, hydro lines, sewer lines, electrical circuits or anything else which may contain nodes and connections (physical or otherwise)
Regarding the difference between the two, it looks like the Network Analyst tools would be better for transportation networks (streets, roads, highways, railways etc.), while the Utility Network tools would be better for utility networks (electric, gas, sewer, water, etc.).
Regarding the licensing, maybe this will help: ArcGIS Pro extensions—ArcGIS Pro | ArcGIS Desktop
Also, this, which indicates that the Utility Network extension is not a default toolset: Use extensions—ArcGIS Pro | ArcGIS Desktop
The Utility Network Management extension is an extension for ArcGIS Enterprise only. Once you have enabled the services and published a Utility Network (water, gas, electric and next year telco) you will be able to use the functionality of the UNME inside ArcGIS Pro. The UNME is not meant for transportation networks.
Hi Lin Han , sorry for the delay in my response, but I was travelling.
The Utility Network Management extension (UNME) is an extension for ArcGIS Enterprise (which includes Server). When you install it you will have additional services for versioning, tracing and diagrams. To be able to use the functionality of the UNME in ArcGIS Pro, you will have to have the UNME installed in ArcGIS Enterprise and a Utility Network published to your Enterprise and the services loaded into ArcGIS Pro. The UNME has a services based architecture and you will not be able to use the functionality without Enterprise (so a complete different approach compared to the geometric network which you could manage in a local file geodatabase).
The idea behind this is by using the services bases architecture you will be able to use the functionality throughout the platform (desktop, web and mobile devices) following the web GIS pattern.
The learn more about how to implement this please visit the solutions website:
... and visit the landing page and resources page: