Wayne,
I wonder why I like the round horns vs the 40 X 90 horns. I think it is because I listen off-axis to the round horns in a small room and they sound quite nice and present a very nice "3-D" imaging. With the 40 X 90 horns in a small room, I find a tad bit too much of upper midrange that seems to take over the music.
So I guess what I am trying to say is that with directional type horns you can set them up to better present the soundstage you like best. With the 40 X 90 horns, they spread across the soundstage to where you on off-axis less often.
Ron