Whisker Litter-Robot 4 vs Whisker Litter-Robot 4 Automatic Litter Box

Buy the Litter-Robot 4 if you have three or four cats or want the longest gap between drawer empties. Buy the EVO if you have one or two cats and limited floor space. The 4 is the larger, more established machine with a bigger waste drawer and a long track record; owners praise its quiet cycles and odor control but some report build quality slipping and occasional mid-cycle stalls. The EVO is newer and more compact, with far fewer owner reports to judge long-term reliability.

• Choose the Litter-Robot 4 if you have up to four cats, want up to about eight days between drawer empties, and prefer a model with years of owner feedback.
• Choose the Litter-Robot EVO if you have one or two cats and a tight spot for the box, and you want the same self-cleaning design in a smaller footprint.