We looked at many Tiffany and Cartier rings set with very average stones. Going with a brand name does not guarantee anything! Going with custom setting of a triple x stone does not mean you are getting a “deal” either but excellent value and something unique.def Tiffany. Its more reasonably priced than some of the others (cartier) and you know the stone is of supurb quality. It may be more expensive than purchasing from blue nile or other retailers, but you know you are getting quality and dont need to haggle, etc. Diamonds are an emotional decision and lack logic all together, so going for a better diamond and a good buying experience is in my opinion better than going for a "good deal."
Who ranks these brands? I think they are simply well known because they spend the most on advertising and marketing and those who feel compelled to buy only name brands have unfortunately fallen for it. These lines certainly have fantastic settings but I agree with other posters...the center stones vary widely in quality. Put the money into the the best stones possible and buy a simple setting. Your taste changes and your first upgrade can be a beautiful custom designed and unique setting.Tiffanys, Cartier and Harry Winston are among the highest 'ranked' brands, but like someone posted above, you can get a stone with the exact same quality for a lower price.
No brand at all. Unless you were to walk around with the box and the paperwork to show it came from a particular brand, nobody is going to care. Pay for what you can see, which is the 4c’s. Branded diamonds are exactly that, branded diamonds, you cannot tell the difference even with loupes, where a diamond was purchased (unless the diamond is laser engraved on a girdle). My biggest gripe about diamonds is that you pay for what you get, and it is more economical to get a better quality stone GIA graded rather than a branded diamond. All diamonds will lose some value over time anyway. HTH