This pillow has a great design to support the neck, I'm on my second one!  However I agree completely with a previous reviewer about the fact I can only use half the pillow!!!  I'm having to replace my second pillow again after 8-9 months.  It gets crushed down, can't support my neck well and I can't use the other half  of the pillow because its too high for my neck!  This is way too expensive !! Half the pillow goes completely  unused but still has to be replaced!
As the difference in densities is "subtle", why not eliminate that selection completely and instead offer pillows with different heights.  That way customers get a pillow they can use both sides of.