The kernal of course has exactly the same functionality as kernels in systemd distributions. What good is that without the user space using the functionality though? A portable init tool will not use any of that... as soon as they do, the portability is gone and they are linux-only.

Systemd-logind delegates priviledged operations like cgroup creation, power management, and such to PID1 (systemd) because that is the process with the necessary privileges and global view of the entire system to perform them. Managing that stuff is the one job systemd-PID1 has, logind is in a layer above and uses the foundational interfaces from the layer beneath it.

Elogind removes that integration by necessity. No idea what it does instead, but going by elogind devs stating that consolekit was good enough and that logind is just a power grab, I doubt they do a very thorough job. That elogind is basically only updated when a new gnome version uses interfaces not provided by elogind does not indicate a very pro-active maintainer team to me.

But you do what you think is best for your systems, I do what I think is best for mine.