LibreELEC is focused mainly on x86 and RPi.
Most of the CoreELEC team is focused on Amlogic, we also collaborate with the OSMC developers who are also focused on Amlogic because of their Vero4K device.
It wouldn’t be appropriate to say which is better.
Our builds consist of the kszaq kernel and numerous patches which fix a number of problems related to running Kodi on Amlogic hardware along with the very latest and bleeding edge version of Kodi.
wrxtasy builds are Krypton (17.6) where as CoreELEC is Leia (18).