Both names are beautiful.
Although
Catherine is a classic, I just don't find it boring the way that I do
Mary and
Jane. I do prefer the K spelling, and we all know that
Grace is a filler middle name, so I'd deduct just a little for those two things, but both combos are beautiful.
I think
Victoria is the most perfect female name there is. (Obviously, as the mother of a
Victoria).
Joy is so nice as a middle name for it, as it sounds best with a one-syllable middle name, and
Joy is not filler and is bright and cheerful.
Your cousins have excellent taste IMO.