Be careful with a manufacturers marketing claim that talk about the maximum pool volume their cells can do. Instead, you should really look at the amount of chlorine they produce when comparing the different model.

http://nsf.org/certified/pools/Listi...submit1=SEARCH

This link shows the tested outputs of systems that are NSF50 approved (independantly tested for commercial standards), and shows the actual chlorine outputs cells are capable of producing.
The CPSC48 produces 1.28 lbs/day (not 2.5 lbs/day as their brochure states), same as the AutoPilot SC-36 (RC-22/35). The SC-48 (RC-42) produces slightly more than the Aquarite large cell (1.45 lbs/day = 66 kg/day), 1.56 lbs/day.
The CPSC36 only produces 0.92 lbs/day (not 1.9 lbs/day as their brochure states).

Hope this is helpful to you.