Hi jal297,
Post #8 here has a comparison between the SleepEz Special and the 9000 and the reasons behind the difference in the prices including that the Special has a pillow bonus instead of the regular 5% TMU discount on all their mattresses.
The only thing that isn’t covered there is the fire barrier. They would tell you for sure but I believe that the SleepEz Special has a viscose/silica type of fire barrier which other than wool would be my preference because it is an inherent fiber without any chemicals (just the viscose and the silica). There’s a little more about this at the end of this article and in post #2 here.
Hope this helps.
Phoenix