Or they couldn't figure out how to program the +200% out from the upgrade and back in from a subsequent upgrade to cannon.
They shouldn't need to, it should be possible to treat it as an all-new upgrade effect like that for any other unit, and there's no issue with upgrading a normal Hwach'a to a cannon. The game shouldn't need to remember that a particular Hwach'a used to be a catapult when it next upgrades. Still, since it wasn't fixed in the last patch there must be some complexity to it.
Dislike: Songhai. While the bonus from barbs is nice, I never pillage when I am taking a city. I like to have everything set up when I move in. I don't always pillage in games when I have enemies but don't take their cities. Even with strong knights I find them trumped with pikes and forest/hill tiles on long marches.
That's not the way the UA works, although it's badly-phrased. "Pillaging cities" = gold you gain automatically from capturing a city, not from pillaging improvements. A large city can easily net you 1,000+ gold as Songhai.
America - same as previously.
Songhai swims in money and human player knows how to use it.
It sounds from a lot of the comments here that many human players don't... I'm very surprised by this; it was here that I first heard talk of the Songhai being one of the game's best civs when I too had thought the UA looked somewhat weak on paper. Playing them I realised that it was true, despite a UU that could be better.
I had a particularly enlightening game with Korea these two days. I had awesome success defending myself against a bunch of warmongers, but I also found how much of a setback Korea's UA is. So get this: you want tech, right? Assign Specialists to your buildings and you get it. However, assigning specialists means stopping the work on some tiles, which in term reduces your effectiveness, which in term reduces your city's food/hammer production, and that in term, lets you grow slowly and produce tech buildings slowly, which affects what? BEAKER PRODUCTION!!!
And yet, you upvote ... Babylon? A civ that's entirely reliant on cramming universities full of specialists in order to maximise the 50% GS generation bonus? Don't get me wrong, Babylon's a strong science civ if less versatile than Korea, but it sounds as though you have yet to settle on effective playstyles for specialist production, which makes voting in favour of any specialist-dependent civ seem odd.
I assume there is a perfect scenario where you have so much food to grow that you won't mind assigning a few specialists to specific buildings, but that happens like once per 20 restarted games. So even though I liked managing to defend myself well and stay on par with the rest, I didn't like how Korea, which is 100% Science victory oriented civ needs much more time to get there than Babylon.
You need to specialise cities - a city which is focused around food production is great for specialists generally. Moreover there are plenty of cities where you'll want to add specific specialists, such as workshop specialists in production cities, because you don't have enough remaining tiles with good production yields, or because you want to specialise in the production of certain Great People. And at higher difficulty levels artist and scientist specialists are essential to keep up the tech race and to keep policies coming at a sufficient rate.
You seem to have the specialisation of the two civs pretty much completely backwards. Korea's benefit works with any specialist type, and just provides free beakers - you can very easily focus on a culture victory, or on production of military units (including Korea's two exceptional UUs) while gaining more science than your rivals in the process. You can heavily focus specialists in a single city to play tall, or spread out across multiple cities (albeit less optimally, due to the food limitation you mention) to play wide. Unless you use Babylon only for the early academy (in which case Babylon just has the mediocre UA "get +8 bpt once you have Writing"), Babylon needs to be pretty purely focused on science to get its benefit.
Finally, the fact that Korea's main benefit is to beaker production while Babylon's is to GS generation means that Korea will have more beakers per turn than Babylon by the time Great Scientists and RAs start popping - and that means Korea gets greater benefits from each of these than Babylon does from each of its Great Scientists. Bottom line: Korea will overtake Babylon in science production in the mid-game, and Babylon won't catch up.
is not situational. 
