For a comparison: look at the diadem of Queen Sonja of Norway in the first post, it has four nice large diamonds in front (the central prong) all others are smaller brilliants. The diadem by Princess Máxima is studded with all the size of Sonja's largest diamonds... The other diadems in the first post all have smaller diamonds.
Unfortunately the diadem from the Mellerio ruby parure gives Princess Máxima a sort of devil's appearance (horns). On Queen Juliana this effect was not so big, the diadem was far more fitting on her than on Máxima.
I hope Gert-Jan does allow me to repost his spectacular pictures... Compare the stones: