Why choose a managed switch over an unmanaged?

Differences between managed and unmaged switches, managed switch benefits.

Managed switches

Characteristics of managed switches with full control and monitoring include:

Can be deployed on a broader array of topologies such as Spanning Tree Protocol, ring, mesh, stacking, and aggregation. These allow for greater redundancy and reliability.
Ease of managing and troubleshooting large networks, through remote management, software-defined network (SDN) management, access to telemetry data showing traffic flow, and even supplying of electric power to endpoint devices
Many security features to control who is accessing the network, monitor for attacks, and help remediate any breaches that occur
Ability to optimize the performance of devices and applications on the network, through quality-of-service (QoS) features that help prioritize traffic and group types of devices that use common services

Unmanaged switches

Characteristics of unmanaged switches with basic connectivity features at low cost include:

Plug-and-play operation that relies on auto-negotiation for settings.
Suitability is limited to simple network topologies, such as star and daisy chains.
Ability to create and store MAC-address tables, making traffic management a step better than using Ethernet hubs.
No distinction in how the switches treat multicast traffic and broadcast traffic, which can cause severe congestion issues called broadcast storms (a problem especially for industrial IoT devices, which often rely on multicast traffic for device-related commands)

As we can see above unmanaged switches are not usually suitable for Industrial environments.

Unmanaged switches are often chosen because of their lower cost. However, with that lower cost comes the inability to manage traffic on your OT networks which will cost more in the long run because of increased downtime and lack of troubleshooting availability.