As the Brits say, different horses for different courses. Based on my experience, a good horn speaker gets me closer to the experience of a live music event than other type of speaker. Given that speakers are typically the largest source of distortion, compression drivers and horn loading are an elegant solution because they have less mechanical movement compared to direct radiators. Planer speakers share this advantage, but aren't capable of displacing enough air to capture dynamics. As with most things, the key is in the implementation and execution.
But there are a lot of drawbacks, namely size, weight, number of drivers (at least 4 for true full-range reproduction). It would be very difficult to live with horns in a small room. I think this is the main reason for horns' lack of commercial success.
My Edgarhorns are superb all around. All speakers are compromised in some manner, but horns, if properly executed, are simply more true to live music.
Regards,
Scott