I've tried and used both. They are both arch, and they both have their uses.

Endeavour is an excellent "arch with GUI" as another user pointed out. However its missing GUI elements which I personally expect from a modern OS like a Package Manager. There are work arounds like Buah, but I found them to not be as polished as having a distro shipped with it.

Manjaro on the other end is also Arch, but with a heavy emphasis on User Experience. The depth and detail their GUI is, means you don't need a terminal if you don't want to use one. Kernel, Systemd, and more has a GUI interface baked in to areas you'd expect them, like in setting.

But their packages being behind means that installing from the AUR can cause issues when the AUR package expects a newer package that manjaro is still evaluating.

For me, I am using Manjaro since I just want a work station that works. And not having to deal with a terminal to fix most problems is something I desire in an operating system.

With that said when I got EndeavourOS to a point where its mostly usable with GUI, there was no noticeable difference in day to day use. I just found it tiring when something broke.