Are sugar grains larger than salt grains?
no. sugar grains are smaller than salt grains
Iodized salt usually is a form of processed table salt, of which the grains are very fine (about 1/8 of a cubic millimeter each). Kosher salt (iodized or not) is salt that is used for koshering meat. Its grains are considerably larger than those of table salt (though sizes of Kosher salt grains vary).
A sugar molecule is quite a bit larger than salt molecules. Why? Sugar is an organic molecule made of Hydrogen, Carbon, Oxgen the ratios and exact structure vary with the type of sugar. Salt is a rock, it's chemical formula is NaCl (common table salt, or sodium chloride), whereas sugar, sucrose being the common table sugar has a chemical formula of C12H22O11.