Both are not directly comparable, there are specific advantages of IoT Central which you may need to consider.
IoT Hub is a PaaS service which can be used with other services to create an IoT solution while IoT Central is IoT Application platform which can be used as-is or extended via companion application. Even addressing basic functionality in IoT Central you will need over dozen other services and you own responsibility to design, manage and administer the orchestration yourself.
IoT Central internally uses multiple IoT Hubs (HA/DR) and bunch of services to bring the functionality that you see in the application. This includes App Service to host the UX, Rules Engine, Fast Storage, API layer, Data Export, RBAC, in-app Multi-tenancy , etc. etc. The key advantages you get -
- Full featured IoT solution with high availability, security, scalability that is available in < 10 secs under 99.9% SLA
- Simplification, easy to connect any device or simulate basic capabilities using the built-in plug-n-play support. Just select any device from the pnp catalog and try it out even before purchasing the devices.
- Create user or app level dashboards with device specific views. Device specific view can be auto-generated with PnP devices.
- Rule creation, alerting and integration with other applications via Logic Apps, Functions
- Data Export functionality to Event Hub, Service Bus, Blob Storage or Web hooks
- Rich Job's interface allowing updating device configurations or firmware
- RBAC in combination with Organizations allow giving specific permissions to user.
- The big advantage is all this is available with a very simpler per device per month pricing that starts as low as 8 cents per device per month ($2 a year) + additional messages https://azure.microsoft.com/en-us/pricing/details/iot-central/
In general unless you already have UX, Storage, Rules engine, etc. elements required for IoT Solution and need to add IoT Hub to ingest and manage IoT devices it will make more sense to start with IoT Central and build with it. It will save time, efforts and you can focus on specific differentiation than build the underlying plumbing and owning the management and sustenance. It is difficult to come to that price point given the high cost of cloud engineers required to support and maintain it.