A major difference is Manjaro has its own repos which has a tendency to break AUR packages, while EndeavourOS uses the normal Arch repos. Endeavour is pretty much just pre-configured Arch so it bypasses a lot of the issues with security and stability that Manhjaro suffers from.
IMO I still think people should just use vanilla Arch so they can customize everything to the fullest but EndeavourOS is a decent option.