I have many pieces from Dior Rose Celeste collection as well as Van Cleef Alhambra, Lucky Spring, Socrate, and Cartier Clash and Love, and they are all very different. IMO,
Dior fine jewellery = looks very dainty (even when you wear something with multiple motifs, rather than looking tacky/over-branded) and adds a touch of femininity. It's rarer than Alhambra or Love, and to me they are more artistic pieces than simply jewellery, therefore you're unlikely to see copies. I have never ever seen anyone wearing the same Dior Rose Celeste 5 motif necklace or bracelet that I have, and people always ask where they are from. The double-sidedness of rose celeste collection also gives you more options. I always wear my earring moon on one side and sun on the other. People sense that my jewellery must be expensive but very few know that they are Dior.
Van Cleef = timeless, easy to wear and surprisingly weightless for its size, you can really wear every day any day without thinking twice about the outfit. Van Cleef MOP is shinier and has more lustre than Dior's, easier to wipe clean as well. But very commonly seen and easily copied, which is why I prefer Lucky Spring and Socrate collection.
Cartier = They do solid gold pieces of jewellery really well. Between the three (Dior, VCA, Cartier) of them, Cartier reminds me the most of modern Parisian women. They did such simple things to solid gold to make them super cool.