Fractional vs Simple distillation
In practice distillation is not 100% efficient: You never get a perfect separation of a mixture.  But fractional distillation is more efficient, so you would expect the product to be of higher purity than that produced by simple distillation.

E.g., if you have a 50/50 mixture by mass of two liquids, you would expect a higher concentration of the higher-boiling-point liquid at the end of a fractional distillation apparatus, which means a smaller fraction of the original mass.