Strange network on iMac 2011

[thisisanacc]

I connect a LAN cable to the iMac and , at the same time, turn on the AIRPORT of it and it connects properly.

I wonder which network the iMac will choose to use in this situation when I connect both. Both network come from the same Modem which simultaneously provides wired and wireless functions.

More interesting, when I use Slingbox for TV on iMac, Mere WIFI connection is even faster than mere LAN connection (mere WIFI provides higher KBPS).

Why?

 

[TEG]

Typically, a Mac will use the Wired connections for data, then if there is a connection interruption or you disconnect the cable, fail over to the Wireless networks.