Trogon said:
The 3 of Cups represents events which involve the emotions to a great degree - hence the spontaneity, the surprise, the love. Whereas the 4 of Wands brings to mind events which have taken energy to put together, have required work and creativity to have been pulled off so successfully.
That's an excellent way to distinguish them! If I may elaborate on what Trogon said:
3/Cups is any loving family gathering--the big potluck, reunion dinner , or the girls night out, or the family picnic. It's to establish FAMILY BONDS. Love, clan, unity, brotherhood/sisterhood, tribal celebration around the campfire. It's enjoying each other's company.
4/Wands, as so many have pointed out here, is a CEREMONY to establish something. So I would say that this is
the wedding because it involves NOT just a party, but RITUAL. Thus, as was pointed out, the wedding party might be 3/Cups, but the actual WEDDING ceremony is most definately the 4/Wands. Another apt celebration for 4/Wands would be an old-fashioned barn-building party, or a dinner to raise money for something. The celebration has a purpose to it other than to just
party. A magical, practical, creative and future-looking purpose. People are there to witness, participate in and celebrate this change, this new beginning or grand transformation!
But 3/Cups, as Trogon pointed out, is completely in the moment. It celebrates things as they are, now, and people, as they are, as you love them, now. No transformations, no barns built, no money raised. Just unity and the delight we all take in being with those we love.