A dog is more useful than a cat... How would a cat fight against raiders? How would a small cat fetch something for you? What would be the use of a cat as companion?

And as others have said... you are not forced to use the dog.

I love cats, but I agree that unless they were mutated to be more powerful or bigger and better at taking direction then cats would not be my ideal furry companion for traversing the wastes.

Aaaaaand now I want a two-headed giant sabre cat to be a companion in Fallout.

Erm... Don't know how to break this to you but there are no cats, cats were one of the first things eaten after the bombs dropped, along with horses. Cats are extinct. Also how is a tabby going to go up against a supermutant? Purr them into submission? although actually thinking about that I would love to see it but yeah no cats. Also dogs are the best and most loyal animal you will ever meet, okay being limited to one breed is kind of boring but also most dogs would be mutts anyway, not sure there are selective breeding groups in the wasteland, hell most places can't even muster clean running water so wasting time and energy breeding specific breeds would be redundant.

As for being constrained by the 'traditions' of the first game in the franchise; The lore for the Fallout Universe is amazingly deep and almost all encompassing it may have been altered a little here and there but mostly it is the basis for all of the games that will ever exist in the series with each game adding a little extra.

Only if I can equip the female version and a party hat on any potential super mutant companion

Hear hear

pee in his boots.

and the cats name would be Piss 'n Boots.

i won't ask where exactly you intend to equip that party hat....... =)

seriously, they won't.

the abandoned tchernobyl area?

all cats. they rule the land. no kidding.

might be fuzzballs, but they're sure survivor fuzzballs

(anybody who ever saw some tiny cat mum putting up with some clueless doberman knows what i'm talking about

I can see maybe having a cat as a pet at your house, but not as a companion to roam the wastes with. And quite honestly, if they did it someone would complain if you didn't have to empty the litter box because it would break immersion.