Let’s talk about diamond shapes. The round brilliant is the most popular shape for good reason: it faces up large, and no other shape can perform as well in terms of brilliance, fire, and scintillation. Rounds are also easiest to predict in terms of performance when you only have its specs, so it is a safe bet if you’re thinking about purchasing your diamond online.
Other shapes are categorized as “fancy cuts”:

(Image from Excel Diamonds)
The second most popular shape these days is the princess cut. Due to the popularity of princess cuts, their performance is also becoming easier to predict based on just specs and numbers. The princess is probably the most brilliant fancy shape; however, the downside is that they look very small for their carat weight (a 1ct round will look much larger than a 1ct princess).
If you want something that will look the largest for their carat weight, go for the pear or marquise. A 1ct pear or marquise usually looks as large as a 1.3ct round.
Asschers and emeralds are step cuts (as opposed to brilliant cuts), meaning they are not cut for brilliance (they don’t sparkle as much). However, beautifully-cut asschers and emeralds can be breath-taking: when you stare down on a well-cut asscher, it can look as if you’re looking down into a pool of clear water. Asscher cuts are really gaining in popularity these days; however, there are two cons to them: (1)they face up very very small for their weight (perhaps the most so out of all diamond shapes), and (2)they show color a lot easier than brilliant cuts so you ultimately have to pay more to get something that looks the same size/color as say, a round.
The cushion cut is what I had originally wanted. As you can see from the picture above, it is shaped like a cushion. There are sooooo many different types of cushions out there: old miner’s, cushion modified brilliant, cushion brilliant, etc. Even within those, they can be cut differently with different faceting patterns. However like princesses and asschers, cushion cuts face up very small for their weight.
With all fancy shapes (with the exception of princesses), you need to see the actual diamond in person and compare them side-by-side because due to the many variations within each shape, it can be difficult to predict their performance based on just specs and numbers. A fancy shape may look horrible on paper but can look great in real life, and vice versa.
Next up: our diamond shopping experience…and some tips!
Also keep in mind that to make a round cut, the diamond cutter has to take a lot more off of the original diamond that they do for a princess.
A princess-cut diamond gets you more carat weight for less money, but they generally look smaller because a considerable amount of the diamond mass is under the stone, not on the face.
Of course, the most important thing (even if you think you’re going to buy online) is to go to a jeweler and try them on so that you can see which ones look best on you.