Ok what is the difference between spherical and flavor disc spherical?

The flavor disc came way after the spherical.  The flavor disc wand was made only as the heater cover for the LSV.  the spherical was just for the SSV, then I realized after like 5 years it worked together, but better.  The flavor disc seals way better because of the conical inside, as well as the bowl is larger.  it also allowed us to go from 2 styles of HFA 2 just one