I usually direct sow....why is Winter Sowing better?
When you direct sow in the ground the seeds are at the mercy of Mother Nature....they can get washed out in downpours, eaten by critters and bug and birds, desiccate in the wind, or rot in the soil.
In a Winter Sowing mini-greenhouse the seeds are in a protected environment. They get the same weather as the seeds in the ground...same temperatures, and the little slits in the lids allow both rain and melting snows to keep the soil moist and the flats watered. But they ARE protected so more of the seeds will survive to germinate in Spring. The germination counts are generally astonishingly high.