Using ethernet network cable is much faster than using a WiFi connection.

So clear and direct. WiFi makes you lose 65% of your average connection. The average of the connections of 100 Mbps is about 36 Mbps real, in the case of 200 Mbps, the average is usually around 100 Mbps. And that the new WiFi standards, such as 802.11ac, offer maximum speeds per band of 866.7 Mb / s. Obviously, we talk about theoretical maximum speeds, since there are many aspects that compromise the performance of WiFi:

Interference, distance, and obstacles:

all these factors compromise the performance of the connection and make it worse.
For example, the existence of electromagnetic waves from other devices, such as cordless phones and other household appliances, can harm the connection. Also, the distance, since it will not yield equal to 10 meters from the router than at 50 meters. And finally, the obstacles. The walls, depending on their material, can attenuate the signal somewhat or much.

Channels and saturation:

The channel used by the WiFi connection can be shared by the connections of other neighbors. This saturation impoverishes the performance, so it is always recommended to look for the most optimal channel possible.