The system that Austin highlights is typical of many power utilities operating at 9600 or even 1200 bps. The ethernet converter I commented about would only talk to the head radio which kinda negates the benefits of ethernet. My "terms of reference" is a municipality with a robust ethernet 900mhz ISM radio network dating from 2005 onward. The beauty of DNP3 via Ethernet is that when links drop on occasion, as soon as they restore the built-in DNP3 buffer is polled and fills in the gap in data. I imagine the same would apply via serial radio. So yeah, seems there's a strong case for serial as well.