Just for fits and giggles I dug a Forerunner 935 out of a box and took it for a sea swim with an F8S47 this morning. Several years apart and several generations of GPS later we can see this:
The blue is the 935 and it can easily be seen how much blockier the track is - less GPS fixes, little accelerometer input - compared to the F8S47. The overall difference was only 100m 1973m for the 935 v 2042m the F8. Not setting out to really prove anything with this other than to show there is a clear difference with the tracking of the 935 v the F8. BTW, both on 1s recording too.