The size of 0.99ct is visually the same as 1.00ct, provided the qualities are the same. However, there’s a price difference of $800 - $2,500 and more depending on quality. For those who are money conscious, 0.99ct is the way to go. On the other hand, diamonds represent love. Being able to say One Carat, makes one feel more warm and cozy. Furthermore, some say 1.00ct holds better resale value when it’s time to sell or trade in for a larger one. My take: If you’re a logical individual and finance is an issue, then the 0.99ct should be your choice. If you’re able to invest in 1.00ct, I think it’s very romantic and it makes you feel good knowing you’re giving her a full carat.