The useful unit is the whole litter system: material, tray size, tray number, location and cleaning routine. Compare comfort and household practicality, then change one variable at a time.
Clumping or non-clumping
Compare daily scooping, full replacement, dust, tracking, texture and what the individual cat accepts.
Sensitive paws and kittens
Start with an unscented low-dust texture and an accessible tray. Seek veterinary advice for pain, redness, straining or sudden avoidance.
Enough well-sized trays
One tray per cat plus one extra is a useful starting point, placed as genuinely separate choices.
Cleaning and tracking
Scoop at least daily, follow the product directions and review tray design and placement before blaming the litter alone.