glad Rio and Chilli got used to their new trays so quickly! I've found it's not so much an issue with smell whether the trays are hooded or not. We got a hooded tray initially to help Tigger settle into better bc we bought the same ones (incidentally!) as the breeders'. In addition to the hooded tray, we've also got 2 trays with no hoods and they seem to prefer it better.
when it comes to cleanliness, I find it's a bit more of a hassle to clean the hooded one bc when they've got traces of soft poo, they wipe it on the sides of the cover as well, whereas with the unhooded ones they wipe it on the lip of the tray. As for smell, I don't really notice a difference - Tigger's are normally less smelly but Nala's can stink up a room within a second of her going!
she even goes as far as to let out a little bit (which really stinks, has been happening since she was a kitten) when she gets a bit of a fright. Her reaction goes - fright, squeak, let out some poo-smelling gas