I'm pursuing the 100 x 100 because I have found the 4430's pattern fits the way I listen. System A in this project was 2370A with a 40 x 120 pattern, and I found it too restrictive immediately. I don't have a "listening room" per se, and often, I'm not the only listener, so a "sweet spot" doesn't apply here. I want everybody on the couch, in the room, and in other rooms (which, often, is me) to enjoy the same fine JBL experience.
Indeed, if I had a fixed HT setup, as Earl suggests, I might make a different choice. The horns (I keep calling the "horns" out of habit, but the "waveguide" term is, indeed, more appropriate, since they are quite flat, not at all what we traditionally think of as horns,) are relatively inexpensive, and I guess having several different patterns on hand might be a reasonable option. TimG is studying a different pattern; hopefully he'll report his findings here soon....