All right, looks like I might need to get the ball rolling.
I prefer the extinguisher over chem (which my phone wants to autocorrect to Chen) spray. Let's look at some scenarios here.
1. Spray: You see the fires coming, and you spray the hull in advance to protect it. That'll take a couple of seconds, during which time you may or may not be getting attacked by other guns. Any components you didn't spray might get covered in several stacks, wasting a few seconds while you extinguish them.
Extinguisher: The fires hit, and you're able to quickly extinguish them. They may reignite, but then you can just wait until they become a problem and put them out again.
2. Spray: You don't use spray in advance. You get several stacks of fires on things. It takes forever to put the larger ones out.
Extinguisher: No change.
This is assuming that they even use flamers, which hardly anyone does. With fires coming from guns like the rocket carousel, there's hardly any difference between the two items, since those fires won't be doing any significant damage anyways. The flare gun is the only really significant fire-inducing gun right now. If you don't predict when a flare is coming, then your chem spray will take way, way too long to put the fire out while the component's health melts. The extinguisher, on the other hand, erases the fire before it can do any major damage.
Any thoughts?