So far I've found the inreach tracks better than the spot. One rudimentary test I did was to have both devices sitting on opposite sides of my dash and logging as we drove from crater lake to my inlaws place in paradise. There were a bunch of gaps in the spot track, like no pings for 40 min when set to 10 min pings. The inreach clocked a location ping every 10 min without fail.
I understand your experiment. It would be better if you repeat it, but this time reverse the units from right to left sides.
I've used various GPS receivers in cars for about twenty years now, and I've discovered all sorts of little things about GPS reception that you never would have imagined.
