do a continuous ping on both hubs' IP addresses, see if you notice a difference. On the slower hub do you have many cloud or LAN integrations? Both of those slowed my hub down.
Also try a different web browser and see if any different results
How long is the cable for the garage/shop? Is there a switch or something between the house and the slow hub? Have you tried moving the slow hub to about the same place as the fast hub?
Thanks. I moved the hub about 20 feet. From what I can tell, the nearby WiFi AP may have been causing some interference (speculation). Moving it seems to have solved the problem.