[jakejm79]

no sense
Mi Box have USB 2.0 port and Wifi AC will be faster than 100Mbps Ethernet

You can't make a blanket statement like that. The advantage with a wired Ethernet connection is that you will normally achieve 90% of the rated speed with no real fluctuations that isn't true of wifi. Also with wifi you are sharing the bandwidth with other devices, if your file server and router support gigabit connections then then you can multiple wired 100 Mbit connections that wont slow things down. Also wifi speeds are very dependent on location, distance and obstructions none of which effect a wired connection.