The Raspberry Pi 3s Ethernet Port is only capable of 100 MBit/s and is furthermore connected to the USB2.0 Chip. For comfortably browsing through Photos of 5 to 7 MB from my mediaserver this is not enough speed.
The Odroid C2 comes with a Gigabit Ethernet connection and “more power under the hood” (as we say in Germany ;). It also provideds a much faster Emmc Slot compared to the mini-sd-card of the Pi.
Download the tar package and unpack it with:
Tar xzvf coreelec.img. gz
then write it to your emmc- or SD card
dd if=/pathtoimg/coreelec.img of=/dev/mmcblk0