I also agree with the people who say that Kaz is both a cat and a dog person. But his two og associates, Inej and Jesper, are heavily divided on the cat vs dog topic.
So one day, as Kaz is scribbling numbers away on his papers, Inej is seated on his window, Jesper is seated on the chair across from Kaz, and they have a conversation that goes like this...
Inej: What a cute kitty! Do you see, Jes? Look at the way it walks on that fence
Kaz: *flicks his eyes at her but remains silent*
Jesper: *snorts* come on, 'Nej, obviously dogs are better
Inej: *offended* dogs are cool, but they never beat cats, you have no idea how intelligent cats are
Jesper: cats are mean and hissy, one can at least have fun with dogs, right Kaz?
Kaz: *absentmindedly* they're useful
Inej: *scrunches her face* well, you aren't required to do so much for cats, they are independant and manage themselves perfectly, they're also great for mice control, don't you think we should get one Kaz?
Kaz: *lifts his gaze to her* you make some solid points, Wraith
Jesper: but, Kaz, you just said that dogs are useful, they could be trained to protect the Slat, so we should get a dog
Kaz: *stares at the wall and blinks into the abyss*
Inej: and then have them bark loudly enough to inform the entire neighborhood and make us twice as visible to enemies?
Jesper: and what of the cat? Have it leap around and knock shit off the shelves?
Inej: it won't once it develops a routine
Jesper: a dog won't when it develops a routine too
Inej: Kaz, you pick, cat or dog? Cat right?
Jesper: No, Kaz, dog! Pick dog!
Inej: he will pick cats, just you see, he would like their personality more
Jesper: no he won't, he'll pick dogs because they are better trained!
*both stare expectantly at Kaz who continues staring at the wall*
Kaz: both have their merit
Kaz: although, Inej does have a point about mice control and quietness
Inej: *smirks triumphantly*