I have only heard the top dog-Strain Gauge and Sussuro Soundsmith carts.They naturally, were amazing. Likely the rest of the line is similar in their price points.
I had the Zephyr in mind when choosing the ART 9. The SS carts are a great match with VPI. At the time, the only reason I chose the ART9 is because I liked the sound of the existing cart-ATOC9III. Figuring the ART9 would improve on the weaknesss of the OC9, it was a gamble that payed off. If I ever get the itch, I would like to try the Aida or Zephyr MIMC.