I’ve spoken with our software team and apparently the reasoning for using 9600 baud is that Arduino Software Serial can have issues going much faster than that, especially when there’s much other code running. We’re planning to update our Arduino examples to work correctly with our latest Ping_V3.28_auto.hex firmware (enabling both 9600 and 115200 baud without needing to change firmware), and change our documentation to say that 115200 baud is possible, but not recommended unless on Hardware Serial.
See the following GitHub Issue for progress:
In the meantime, if 115200 is working without issues for you then you’re welcome to continue using it, but if it is having some problems then I’d recommend either
changing to an Arduino with additional hardware serial ports (e.g. Arduino Mega), and using hardware serial instead of software serial OR
connecting your Ping to your computer via a BLUART (or some other USB to TTL Serial converter), and updating the firmware to Ping_V3.27_9600b.hex, after which you should be able to use 9600 baud software serial in your Arduino script. (Detailed instructions with screenshots here)