A:1. Flexographic printing required paper in roll. Offset printing required paper in sheet
2. The technical of offset printing is mature than flexographic.
3. Design mould different: flexographic plate is made of resin material, it's expensive, as usual cost usd100/color; but Offset required a digital plate. it's cheaper, as usual cost usd30/color.
4. The ink of flexographic printing is water based, blend by water, clear by water; so it's no pollution. Ink is Food grade. But generally, the ink of Offset printing is gas/oil based. Blend by oil, clean by gas/oil, so it's pollution, not Food grade. Certainly, there has food grade ink for offset, but high price than Flexographic.