I've used both, and moved from OpenHAB to HomeAssistant around 4 years back. Both required some upkeep from time to time, but HomeAssistant lowered my maintenance and debugging time. The OSGi architecture used in OpenHAB felt pretty clunky running on a small Raspberry PI or similar system compared to HomeAssistant. OpenHAB always felt like overkill for my simple use case of a small home containing few sensors and lights.