You want cats because they're cats, of course! Who doesn't want a cat?
As of now I don't want to take them into battle, because they're forced up front, but they can be useful in base defense as a roaming scout. While a dog's Aye ability can cover a larger area, they can't get the vertical placement on their own, while cats passing by can tell you not only where the enemy is within their range, but what enemy it is and which way it's facing, as if you actually saw it.
But mostly just because they're cats.