Oval cut diamonds were created in the 1960's by Lazare Kaplan, and are a modified brilliant-cut (like virtually all round cuts). Since both oval and round cuts have a similar brilliance and fire, the oval cut is the preferred choice of customers who enjoy the look of a round diamond, but seek something more unique.
Due to their elongated shape, oval diamonds create the illusion of greater size. Their shape can also make the wearer's finger appear slimmer and longer, which is often a desirable effect. Preferences vary widely for how slender or broad an oval cut diamond should be, so choose according to your personal appeal.