#1What each protocol is genuinely for
MQTT is a lightweight pub-sub transport. It is excellent at moving data efficiently across constrained networks, but it knows nothing about the meaning of that data. OPC UA is a richer information modelling protocol with a strong type system, security, and discovery built in.
#2Where MQTT (and Sparkplug) wins
MQTT shines for high-cardinality, lightweight telemetry where the cost of encoding semantics is more than the value gained. Paired with Sparkplug, it gains structure and birth-death notifications without losing efficiency.
#3Where OPC UA wins
OPC UA dominates where richly typed information models and secure machine-to-machine interaction are the priority — between PLCs, between MES and SCADA layers, and in environments that demand certified interoperability.
#4Why most factories end up hybrid
We typically deploy OPC UA between control systems and the unified namespace at the edge, and MQTT (with Sparkplug B) for moving aggregated telemetry to the cloud. The edge broker becomes the translator and the policy point.

