I have two boxes, one for each cat. A small one for the little cat and a big one for the bigger cat but guess who uses which one? Yep. Big poos poos in the little one and vice versa.

Also I have watched Simon go and he hangs his booty over the edge to the outside sometimes. My Sammy would scratch and hang ten on the edge but his booty was facing inward.*

Also a big box may be too heavy to clean when it gets full to dump the litter.

*Just checked Simom's claws and he has only four so Sammy would hang eight. Dont know why I thought they had five claws??? Never thought about it. LOL