I have the regular JUC (no diamonds) and I love it! I never considered getting the diamond version because my partner and I bought each other one as a gift (plus the price was a bit steep for my liking) - it is stunning though!
Based on this thread and what you have written so far, I think you should get the JUC with diamonds. Yes it’s expensive but I can tell your heart really wants it - it’s just the price that is holding you back. I’m exactly the same - I would prefer two jewellery items over one but it’s luxury and it’s Cartier. As long as you get, wear it everyday and it makes you smile, then I believe it is worth it.
But I do follow that mentality of “When in doubt, don’t” so please make sure you really want the item before pulling the trigger. Have you considered selling your current small JUC? That might help offset the extra 5K.
Also, think about your long term jewellery wishlist - do you really need multiple bracelets, rings, necklaces etc? If you can cull some items, that might make dropping the extra 5K less painful.