Pictured below are most of the popular diamond cuts. Round is not shown because it’s shape is obvious, but it accounts for a whopping 80% of all diamonds sold. All the other cuts put together equal only 20% of all diamonds sold. A round cut is by far the most brilliant of all, and if cut well, the only one which will keep 80% of its sparkle when dirty. All other fancy shapes will loose a minimum of 40 to 60% of their sparkle when dirty. A round cut is usually 7 to 20% more expensive than most other fancy shapes because of this and other factors. As far as resale or trade in value , a round is by far the best cut for value retention. When shopping for fancy shape diamonds a person might notice a even larger than 7 to 20 % difference in price compared to rounds, as example a cushion cut 1ct. SI1-H quality might sell for 30 to 50% less, etc. This is not due to just the shape, it is usually due to a too deep or too shallow of a cut. A poorly cut a diamond will still look fine when perfectly clean and with tons of light shining on it, but when you get a cheap diamond home under regular lighting and get it a little dirty, it will die and loose most of its sparkle. They end up looking like a fake does when it gets dirty, and this is truly why it has a much lower price. All the diamonds in the photos are extremely well cut examples and will only get more areas of a watery appearance or areas where there is no light being reflected back to your eye when the cut becomes lower and lower quality.