Are they just two sides of the same coin or two things that entirely different? I see there's a lot of relation and crossover development?
What is the difference between Solus and Serpentos?
SerpentOS, a modern linux distribution with a new packages manger, its very different from the traditional. Solus want to base the solus 5 version on serpentOS, because that means modernize the solus tools and the whole system paradigm and also, both distros save work by developing the same tools together
https://getsol.us/blog/
There's some good history here, and where they aim to go. Start with a new voyage.
two different OS's. not the same. separate.
that is, when one officially becomes an OS.
they may share some architecture down the road, though, via partnership.
--cliff notes version
brent two different OS's. not the same. separate.
I think of it as somewhat akin to the distros that are based on arch, or red hat, or suse. One provides much of the infrastructure, while the other makes it more usable. I'm optimistic that the result will be very well integrated, due to Ikey's involvement with both for many years. I'm quivering with anticipation! 
So is it fair to say that Serpent to Solus is like Ubuntu to Mint? Two separate distros that share the same package manager (and other things)
It's like going into a black hole. Will you emerge in the end with something wondrous or just get crushed to dust?
Lol. That's enough beer for tonight.
- Edited
pacer 
I don't think Serpent is using eopkg at all.
I don't know about Ubu to Mint either.
Solus is a day in day out active distro. Serpent is mostly in its development and not an active distro yet.
that's how I'm seeing it anyways.
edit: the people involved with both have known associations with each other going back over a decade; maybe shared philosophies and ideas too. So there's that. Serpent inventions will have a big role in Solus architecture but Serpent itself still being built as an OS.
again, my 'take'
brent I don't think Serpent is using eopkg at all.
Serpent will use the moss package manager. Many of the same ideas that originally went into eopkg (and its underlying infrastructure) are also present in the Serpent tools. It should be pretty familiar to anyone who's been around Solus for a while.
A fair question to ask then is "if the underlying ideas are the same, why develop new tools at all?" To which I would reply:
- The old tools carry a tremendous amount of tech debt, and that causes a lot of headaches
- Not all of the ideas are the same. Serpent tools have features that no one had dreamed of when eopkg was being designed.
My understanding is that Serpent will be the upstream to Solus, meaning that all the cool new stuff will come to serpent first, be tested, tweaked, and validated there, and then pulled into Solus once it's ready for general consumption. Sort of like how we do our unstable and stable repositories today.
infinitymdm That's what I was getting at. I guess the big question is, why use Solus over Serpent or vice-versa? What will be the key differences?
I'm cautiously optimistic about the solus and serpent rebase, even though it's a long term future plan and won't happen any time soon.
pacer why use Solus over Serpent or vice-versa? What will be the key differences?
What I've read seems to suggest that Serpent will be more developer-focused, whereas Solus has always been and will continue to be focused on your everyday desktop user.
As far as "key differences" — who knows? Only time will tell. I suspect Serpent and Solus will look pretty similar (maybe even near-identical) at the initial Solus V release, but over time the differences will become clearer. Or maybe there will be a clear distinction from the beginning. Who knows? It's an exciting time!