Fiberglass blow in: Great for walls and other sealed cavities. but packs down over time. Not the best choice for attics. Several dangerous chemicals are present. Some are very toxic. Absorbs moisture, must be sealed from the environment. R 3.7 per inch.
Cellulose Blow in: Pulp. lots of chemicals in this stuff. Settles quickly. Easily contaminated. Absorbs moisture, must be sealed from the environment. Absolutely the worst Insulation. Looks like shredded newspaper. R 3.6 per inch.