My lady cat produces small, delicate wet patches when she has a wee and her poo is not smelly - she eats a lot of dried food. What she produces is quite firm and as she is a long haired girl this works out okay - a cat with a dirty backside would not be fun to be around.
Her brother/sparring partner floods the litter tray out when he has a wee and when he has a poo it stinks the house out, I have to wait until the smell dies down before I can go near the tray. He eats mainly wet food and I have always presumed that this is why is stinks so badly. He takes ages to dig in the litter tray, then dig again and then he has to wipe his paws clean on every surface in the bathroom.
Merlin (lady) won't use the loo if anybody else is in the bathroom - even if it is just Frankie perched up high on his birdwatching shelf. Frankie is a typical 'bloke' - I had a workman fixing something in the bathroom and Frankie just wanders in and uses the litter tray. One male friend was actually 'using the facilities' when the door slammed open and Frankie walked in and went to the litter tray for a wee.
They are very strange animals.