Popular Mechanics sets out to find out, using boxes filled with sensors. There’s no clear winner.
Since I ship and receive a lot of books during the year, this is a topic of some interest. Since I’ve had many books shipped to me damaged in transit over the years, I always pack the books I send out on the assumption that they’ll be treated with the same gentle care the gorilla gave that American Tourister suitcase:
So everything I mail usually has at least bubblewrap around the book in a bed of packing peanuts inside a sturdy cardboard box.
However, the test seems to have concentrated on overnight and express service. I would like to see if trhere are any differences with the way Media Mail or FedEx Ground. (Remember that FedEx Ground used to be Roadway Package Systems, one of the most incompetent shipping companies ever. They’re improved a lot since the RPS days, but as far as I can tell, they’re still not up to the level of regular FedEx. (And DHL no longer serves the American domestic market.)
(Hat tip: Instapundit.)