Mrdecibel,
While it is hard to separate out the sonic influences of other aspects of a horn’s design, I’ve heard replicas of classic designs where the primary difference was the material used, which means the big difference is resonance behavior. I recently heard a wooden replica of a Western Electric 22A horn that I liked more than the original and other replicas I’ve heard.
What has been hard for me to understand are the notable exceptions where the horn rings like mad yet sound very good. The Western Electric 16A is such a horn. It is spectacularly massive and made of huge, thin metal parts (you can walk into the opening by crouching just a little bit). When the music stops playing, you hear a distinct echo that takes more than a second to fade away. Despite the echo, the sound is not muddy or distorted and the sense of ease (lack of strain) and the large scale of the image is unmatched. It took me quite a few listening sessions to overcome my initial prejudice from hearing that loud echo.