Shape and cut quality are different
Round, oval, pear and emerald describe outlines or cutting styles, not a universal quality ranking. Within a single shape, proportions and facet execution can produce very different appearances.
Brilliant and step-cut patterns
Brilliant-style cuts use arrangements that create many flashes of light. Step cuts such as emerald and Asscher display broader, more geometric reflections. Neither character is automatically better: it is a design preference that should be assessed on the individual stone.
Length-to-width ratio
Divide length by width to describe how elongated a stone is. Compare that ratio with actual millimetres. A ratio describes the outline, not brilliance, and equal carat weight does not mean equal visible area.
Choose in context
View candidates on a hand or at their intended scale. Check the symmetry of the outline, visible inclusions and dark areas as the stone moves. Consider how a jeweller will protect points and corners, and confirm the actual report measurements.
Sources and further reading
This English edition draws on the source material referenced below.