For maximum performance, Ethernet is recommended. The Ethernet on SHIELD supports 10/100/1000 Mbps. Once Ethernet is connected, SHIELD will disable Wi-Fi and switch to Ethernet.
For networks which don't support DHCP, the IP-related settings can be configured in Settings > Network Settings > "Ethernet."
For the best Wi-Fi experience, a 5 GHz dual-band 802.11 AC/N MIMO router is recommended. These routers are capable of operating in the 5 GHz band to prevent interference due to 802.11 wlan/non-wlan wireless radio sources that operate in the 2.4 GHz band.
When setting up your Wi-Fi, it is recommended to scan the wireless environment and choose a less "congested" channel for the AP on either band. Configure the AP in "Auto" mode and "Auto" channel width (This field has different names depending on the AP vendor. Some call it "up to speeds" or "supported speeds."