I think that this would depend on other aspects of your setup. If you have a high speed fiber connection to your router, and you are surrounded by other peoples routers, ethernet will improve your ping times. If you have a bad copper connection to your router, and no other Wi-Fi hotspots nearby, then ethernet might be improving away from the bottleneck. Try pinging another device on the same wifi network, vs pinging an external site.
I think that this would depend on other aspects of your setup. If you have a high speed fiber connection to your router, and you are surrounded by other peoples routers, ethernet will improve your ping times. If you have a bad copper connection to your router, and no other Wi-Fi hotspots nearby, then ethernet might be improving away from the bottleneck. Try pinging another device on the same wifi network, vs pinging an external site.