Wireless convenience or a cable
Wi-Fi connects devices by radio, so you can move around. Ethernet connects a device to the router or switch with a cable. Phones and tablets usually use Wi-Fi; a desk computer or television can often use either.
Compare on the same device
Pause other downloads and test once over Wi-Fi, then with Ethernet connected to your router. Disable Wi-Fi for the wired test. Use the same test server and compare download, upload and latency. A large difference is a reason to inspect the home network.
Choose for each device
Use a cable where a stable desk connection matters and a safe cable route is practical. Keep Wi-Fi for devices you carry between rooms. Check the speed supported by the router port, network adapter and cable before replacing your internet package.