I like Hwachafish more than the Blenderfish, mainly because you only really need that one burst hwacha to disable most of a ship and then it has to rebuild more than just one balloon. In my opinion, the hwacha disable shows effect much quicker than when a carronade destroys a balloon. Pyramidion shooting your ally? Instantly disable it, maybe ram it too and use some side guns. Ship running away from you? It will probably lose 2/3 engines, enough to catch up.
I like to say that the hwacha is more effective, because you can actually destroy the enemy guns. For example a long range Galleon is trying to snipe your ally, that carronade will not make the enemy lumberjack lose arcs. Sure you can ram that Galleon, but you could also use a side carronade on that Hwachafish or gatling to get a quicker kill.
The thing where it can only destroy front guns of a Pyramidion is actually something where it is better than the Blenderfish, because the Pyramidion can easily disable the heavy gun, and for me it is much easier to destroy the front guns than the balloon, so I see hwacha as more effective here, it also not impossible to destroy one side engine too.
The Hwachafish doesn't "hard"-counter anything (and carronades do not beat everything, but that is probably just me), but I say it makes ships more immobile. When a Blenderfish keeps destroying the balloon of the enemy, the enemy can still have some guns shooting back (e.g.: loch mines, if anybody does that; harpoons; the enemy's carronade) or even use terrain to make it harder to maintain carronade arcs. The Hwacha fish needs to hit with one good clip and the enemy is not going anywhere and not shooting anything, it can also support in long range!