Since the last update, a large OmegaPaw box has joined the setup. Right now I have a regular (really should be small) and a large OmegaPaw, and the Stylette UltraSweep.

Observations so far....

• The noise of the Stylette seems to have scared the crap out of the cats. For about a week it was totally unused. I picked up some "Cat Attract" scoopable litter and put that in Stylette, and it is being used again.
  
• It's entirely too easy to dislodge the collection grid on the small OmegaPaw by thumping the bottom too hard (which you need to do to remove clumps).
  
• When they say to spray the bottom of these things with a non-stick cooking spray, they really mean it.
  

More updates and conclusions to come shortly.