So I wouldn't write off Sots2 just yet.
I would, I was willing to give it time and see what happened after the unarguably disaster state it was in at launch, but now, with many of the features in the game and it being generally playable, I've come to the realization that the game is a lost cause. There's still a chance some major UI refinements and other improvements could still turn it around, but overall I'm still not finding the game much more enjoyable to play than the garbage version that was released.
It's even worse when considered a sequel, where ideally the goal is to improve upon the prior game. Instead, I'm still finding literally everything changed for SOTS2 was better as it was before, with the possible exception of the combat system which gets points for being pretty, but is still a pain and the ass to actually use thanks to a crap interface, which goes for the rest of the game as well.
Anyways, I suppose that since my biggest gripe with the game at this stage is the UI, pretty much everything is irritating as hell to do, thanks to most tasks requiring excessive use of poorly designed menus that still seem to hang up for a second or two while loading what amounts to nothing, that sort of stuff could theoretically still be fixed (although my faith in the devs at this stage is minimal). My concern now is how long they can actually keep working on it as a main project, I can't imagine sales were all that great, especially once reviews of the release version got .
Perhaps that concern is unfounded, as I'm surprised it's still being worked on as it is and they have said they'll stick with it until it's good, but like you said, SOTS 2 and ES feel at about the same stage of beta testing, if anything, I'd say Endless Space is further along. The difference is that SOTS2 is actually released, for what, 8 months now? The reviews are out there, the game has been showing up for under $10 on Steam sales for quite some time, are they really going to spend the next year on a project that isn't likely to merit the expense?
I hope they do, but my expectation is that at some point, they'll start working on DLC / expansions to sell in order to justify additional development, which is fine, if they actually sell. If the game isn't in good enough shape by that time, and given the bad press it already has, I'm not so sure they will. And from there, hope fades fast.
TLDR: SOTS2 still isn't in good enough shape for me to consider actually recommending to a friend to give it a try, but Endless Space is looking pretty good (although hardly groundbreaking either, pretty generic gameplay wise, just nice to have a modern entry in the genre and they're doing a great job with the UI, minus a few tweaks I hope to see yet) decent enough game in it's current shape and only just starting it's official beta phase now.