Don't think I can do an ethernet check because my ethernet connection on my iMac has been next to useless for years now and I have been using only the aiport card. I decided to instead compare my iMac to my son's iPad.

I took two readings for each a few minutes apart.

iMac 1st reading: ping 11ms download 15.11Mbps upload 1.90Mbps
iMac 2nd reading: ping 12 ms download 3.01Mbps upload 0.97Mbps

iPad 1st reading: ping 18 ms download 18.57Mbps upload 1.85Mbps
iPad 2nd reading: ping 20 ms download 14.58Mbps upload 1.95Mbps

The second Mac reading (which was very near in time to the 2nd iPad reading) seems pretty conclusive maybe?
We are what we repeatedly do - Aristotle