RebornOS seems to have a system configuration utility, more DE/WM options to choose from and a different overall style. EndeavourOS prides itself as being terminal centric, while RebornOS allows the user to configure the system graphically with their 'RebornOS Fire System'.

As an advanced user these are largely unimportant differences, but as a newbie there might be an appeal to choose RebornOS.

EndeavourOS uses dracut instead of mkinitcpio (whereas Arch Linux uses mkinitcpio). EndeavourOS brands all its desktops for online installation. In contrast, RebornOS made the choice to stick close with Arch Linux, with no branding for desktops installed online, uses mkinitcpio like Arch Linux, only deviations being fixes for problems that Arch Linux refuses to resolve - broken default themes on Cinnamon, MATE, and UKUI, the possibility of black screen on boot for Nvidia hybrid GPU, etc.