what do horns sound like

how do they compare to cone speakers

The problem with horns seems to be that they are too big to be able to acoustically disappear. Smaller speakers tend to do it better but the smaller you go the less power and bass you get

field coils are the only dynamic speaker tech that keeps up with the speed of ESLs.

not really. Most people can't hear anywhere near 20khz. Having a driver that goes faster than that is pointless if you can't hear it. 

If all horns were really as bad as this similistic demonstration indicates, none would survive in the marketplace. Nor would a company like Magico be using horns for their limited-edition top-of-the-line model, as dweller pointed out.

But horns are far less popular than cones. They haven't achieved much success in the marketplace. Most high end speakers are using domes. If horns were superior, that wouldn't be the case. 

 I think the problem with horns imaging is that the first crossover is usually in a terrible place at around 400 Hz. Remember middle C is 256 Hz so this is smack in the middle of the midrange where our ears/brains are extremely sensitive to phase

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400hz is well below the 2khz area which is the most sensitive area. 
400hz is low midrange. The wavelengths are too long for phase issues to be relevant. 

Horns are too big. The polar response of a horn is therefore abysmal. Thats what my instinct tells me. 

it seems to me that the initial premise for its existence is merely based on trolling

You could say that about any discussion on here. Audiophiles rarely agree about anything. Are we all trolls because we all disagree?

To fill an auditorium with loud sound, effortlessly, with sometimes several hundred people attending requires horn-loading, preferably down to at least 80Hz where that sense of ease and visceral impact is so important. Direct radiators would strain wildly and eventually crumble trying to achieve this, unless the driver count could be doubled by several factors - and it still wouldn’t sound the same

A hifi speaker is not designed to fill an auditorium. Its designed to produce holographic imaging, and high fidelity and quality sound.
A horn is not designed for this, its designed to go loud.
Direct drivers already go loud enough to cause hearing damage so there is no need to use a horn to go even louder.
I dont see any evidence that horns provide superior sound quality. Quite often we hear that horns are actually pretty colored. We dont hear that kind of criticism with direct drivers so there is no free lunch.

A horn is not a panacea. It seems to me a fallacy that horns suffer less distortion due to less cone motion. The most cone motion occurs at the bass frequencies where ears are least sensitive to distortion and horn size becomes increasingly impractical. The motion of the air will still be high at the horn exit even if the cone motion is low. I’m not an expert but thats my feeling.The coloration of horns is a frequently mentioned point. Clearly there are some issues.

Horns still suffer from box coloration as far as i know.

There was no desire to educate yourself on how a horn sounds to some. You made that painfully obvious as the post progressed

This discussion is educational for all of us. It doesn’t mean we have to agree. You learn by asking questions and provoking thought.
This hobby is full of controversies theres no need to manufacture any. There will be more nuggets of wisdom from me coming soon.