Back in 2010 Glenn Derene compared UPS, FedEx and USPS to see which delivery company was the most careful with packages:

• Packages sent by FedEx suffered the most drops while those sent by USPS faced the least.
• Across all carriers marking a package as ‘fragile’ led to rougher treatment of the box.
• A USPS package deals with an average temperature change of 32 (presumably Fahrenheit) degrees. A FedEx package is exposed to temperature changes of 26 degrees.

Click here to read the comments of the three shipping companies, graphs that illustrate the conditions that the packages experienced and more.

Source: Popular Mechanics