Your answer is in the Ford F150 brochure. You can get one online or at the dealership. Turn to the section in back with the "packages". It explains exactly what is included in each package.
I have a 2010 F150. In the 2010 brochure, both the regular tow package and the max tow package have an upgraded radiator, trans cooler, wiring harness, and hitch.
The Max package has a stiffer bumper, stiffer springs, sliding mirrors, a brake controller and a heavy duty front eye bushing.
Packages for the new trucks will be similar. I cheaped out and upgraded my springs with Timbrens. No regrets.