The center stone in your diamond engagement rings is considered as the symbol of your love and commitment towards your partner. Hence, it is the most important factor in your sparkler.
For a diamond cutter, round diamonds are great to work on, since the main facets can be cut at exact angles. For diamonds of other shapes, this does not necessarily hold true.
Due to their pointed edges and vulnerability to damages, the marquise-shaped diamond ring needs extra care. Protecting the stone is fine, but you also have to clean it occasionally, so that the diamond ring does not lose its shine.