I want to measure the speed of LAN vs WLAN on my Dell XPS 15 (W 8.1).
It's clear that my Gigabit-LAN is faster than wifi, but by how much?
I use LAN at home, and WLAN when I'm away.
Does a program exist to compare the two?

It takes quite long before the computer "sees" the "new" LAN connection.
LAN is through a USB3.0-LAN adapter (the Dell has no LAN socket).