IMO, the "perfect" litter is any one the cat will use, ha ha.

I use Tidy Cats Scoopable. Have for 11 years. Target has it on sale very 6 weeks for 28 cents per pound. With 7 cats, I use a LOT. Haven't had the problem Jazzcat mentioned with the mucky layer, but then I keep it at least 3 inches deep, often more.

When i lived in a napartment ont he 3rd floor, I used SWheat Scoop, it is lfushable and was very convenient in that 3rd floor walk up. but Mr. Amber Cat didn't like it and refused to use any box that didn't have Tidy Cats.