Interesting thread at the start.
I found myself feeling too confined in many models with what I call "overmolded" seating, where you have a seat edge jabbing you if you don't sit as it was designed.
I personally like to adjust my seating position to have jets hit areas where I may have a knotted muscle, etc with less concentration on other areas.
With many of the more popular models, I couldn't do this, and like a more open plan. Also, I have too many barriers and obsticles in my day to worry about them once I am home, relaxed, and in my tub.