Looks quite neat, though perhaps just a little more complex than systemd service files, I guess they essentially boil down to similar things.

Where systemd has one file with a bunch of settings in, this is split into a directory of single-purpose files in s6. I'd hesitate to call it "better", but from a surface reading it seems roughly equivalent from a usability perspective.

According to the author, Laurent Bercot, the code for s6 is much cleaner than the systemd code. For anyone curious I guess the best way to find out is to compare and make a judgment of one’s own.

While I appreciate clean code when I have to work on it, it's somewhat orthogonal to my requirements when we're talking about running systems rather than building them.

I guess it could be preferred as a second-order factor.

In some ways yes, in other ways no. I've looked at both, and there is always a certain amount of "ugliness" that comes with writing low level C software for Unix.

I would rather have complexity in the engine code than in the unit files. A clean implementation is less important than a clean interface.

I'm not familiar with s6 myself. But - the choice between a single file or multiple files in a directory is a relatively minor issue in the overall scheme of things. i.e. if s6 is "better" or "worse", it's not because of this fact.