VS2 vs SI1: which clarity should you actually buy?

Brilliant cuts under 1.5 carats are the SI1 sweet spot. Round, oval, cushion and pear facets scatter light so aggressively that a well-placed inclusion disappears into the sparkle. The stones to pick are the ones whose inclusions sit near the edge of the table or under where a prong will go, and whose inclusions are white and wispy rather than dark crystals. That is why the rule is to judge the stone, not the grade: ask for the 360-degree video or view it in person, check the face-up view at normal distance, and buy the specific SI1 that happens to be eye-clean.

On lab-grown diamonds the saving is real but modest, a few hundred dollars AUD on a 1 carat stone. On mined diamonds the same grade gap is several times wider, which is why SI1 hunting is more popular there.

Three situations: step cuts, larger stones, and buying unseen. Emerald and Asscher cuts have broad, open facets that act like a window into the stone, so SI1 inclusions that a round would hide sit in plain view. Above about 1.5 carats every inclusion scales up with the stone and gets easier to find. And if you are ordering a stone without seeing the exact diamond first, VS2 is the grade where "eye-clean" stops being a gamble and becomes the default.

Either grade beats overspending on clarity you cannot see. If the budget question is VS1 versus VS2 rather than VS2 versus SI1, we cover that one separately, and the answer runs the same direction: buy the grade the eye can verify, and spend the difference on cut.