Have you experimented with this? Wireless can be subjected to all sorts of interference causing a reduction in speed.
I have experimented with my own set-up and have found that having the router plugged into the BT socket with a metre-length cable and our desktop PC's connected to that with ethernet cables gives higher speeds than running them wirelessly. Have also tried this with laptops. I do also have 3 laptops that operate wirelessly and they function well but not at the same speed as the two desktops.