Well, that depends on what you’re looking for. Generally, the GIA and the International Gemological Institute (IGI) are both highly-respected gemological laboratories.
However, IGI is more affordable and has a wider range of price points. But some jewelers find the system to be too lenient – so don’t expect IGI diamonds to maintain their value as well as GIA ones, for example. In contrast, GIA is more popular because it’s a more detailed system that gives you a better understanding of a diamond’s properties.