If you put the two together, you wouldn’t even think they were from the same plant! The same goes for their texture and flavor. I like baby kale for salads like this because it is soft, easy to eat and the flavor doesn't overpower the fish. But regular kale is totally fine too! Just note that it will be much denser, with a stronger, more bitter flavor. To soften it, try massaging it with your hands, or quickly blanching it (then drying).