https://diamond-tap.mystrikingly.com/blog/why-is-round-cut-the-best

The cushion cut contains 58 facets as well, although they are larger than those on a round brilliant. Inclusions are more noticeable in larger crystal phases, but the diamond has more fire. The playful spectrum that develops when light bends as it moves out of the stone is referred to as fire. The design lets more light to get through, resulting in an excellent range of colours. It also implies that the cushion cut might better conceal colour.