Rolling saves more space. Packing cubes save more sanity. The honest answer is to combine both.
Rolling clothes compresses them tighter than folding or loose stacking, with about 15 to 20 percent space savings on typical garments. Cubes add organization and stop items from shifting during travel, but they do not compress clothes on their own.
Roll each item tight, then stack the rolls inside a packing cube. The cube holds everything in a rectangular block that fits luggage efficiently, and the rolls keep wrinkles down. For bulky items like sweaters, a compression cube beats rolling alone.
See: best packing cubes and how to fold clothes for packing.