Huh? I didn't know the defaults have changed...
In fact, looking at the relevant lines of the driver code...
src/calibre/devices/kindle/driver.py -- line 289
Code:
FORMATS = ['azw', 'mobi', 'azw3', 'prc', 'azw1', 'tpz', 'azw4', 'pobi', 'pdf', 'txt']
Sure looks like MOBI is prioritized over AZW3 to me... actually, I am surprised AZW3 is listed at all, if that means it will be sent to the Kindle
2/3/4/Touch/Paperwhite/Voyage.
EDIT: This is entirely deliberate, see
https://github.com/kovidgoyal/calibr...e692bce5bab7c6 (dated September 2012)
"Kindle driver: Prioritize sending MOBI over azw3 on e-ink devices so that people with older models can convert AZW3 to MOBI and just click send to device"
This change has not been reverted.