Pine shavings are thinly sliced pieces of wood, nearly thin as paper. They fluff easily. Being thin, they dry fast. As long as they are not staying wet, they don't compact. Wood dust is similar to flour, in my mind, and pretty much useless in a coop. Wood chips can be the large granules that come off of a chainsaw, or the ragged chunks that come from a wood chipper.
The residue from a chain saw is slow to dry. The product from a wood chipper is too variable in size and consistency to suit my needs in a coop. It would need to be dried for quite some time to be useful. It can work well in a run.
I like pine shavings because they come compressed in a bag, clean, and ready to use. I keep the unused portion in storage. The shavings are easy to turn over in the coop and nest boxes. The work well once shoveled into a compost heap.
Chris