Honestly, SMF is superior to SystemD and it’s ironic it came earlier (and, that shows based on the fact that it uses XML as its configuration language.. ick).
However, two things are an issue:
1) The CDDL license of SMF makes it difficult to use, or at least that’s what I was told when I asked someone why SMF wasn’t ported to Linux in 2009.
2) SystemD is it now. It’s too complicated to replace and software has become hopelessly dependent on its existence, which is what I mentioned was my largest worry with a monoculture and I was routinely dismissed.
So, to answer your question. The argument must be: IllumOS over Linux.
SMF is OSS. The CDDL is an OSI approved licence. I'm not aware of any reason one couldn't readily ship user mode CDDL software in a Linux distribution; you don't even have the usual (often specious) arguments about linking and derivative works and so on in that case.
Maybe 15 years ago, not by a mile now. systemd surpassed SMF years ago and it's not even close now. No one in their right mind would pick SMF over systemd in 2024.
I regularly pick significantly less featured init systems over systemd whenever it is feasible, because systemd and it's related components have caused some of the largest amounts of work for me over the past decade.
I don't really want to litigate the systemd vs. everything else argument, but as someone that has issues with systemd but is not particularly in love with sysvinit derivatives, I wouldn't mind SMF as an alternative.
The fact that its less opinionated about logging and networking and doesnt ever force any reload of itself are all reasonable reasons to prefer it.
You don’t lose socket activation or supervison. SMF is designed to help work in the event of hardware failure too, which systemd definitely cant handle.
However, two things are an issue:
1) The CDDL license of SMF makes it difficult to use, or at least that’s what I was told when I asked someone why SMF wasn’t ported to Linux in 2009.
2) SystemD is it now. It’s too complicated to replace and software has become hopelessly dependent on its existence, which is what I mentioned was my largest worry with a monoculture and I was routinely dismissed.
So, to answer your question. The argument must be: IllumOS over Linux.