Goce from mp3Car shows the advantages to the p5USB hub
http://store.mp3car.com/DC_Powered_4..._p/adt-015.htm

Features include:
Take voltage from 7-32 volts
guaranteed 500 mA to each port.
Each port has it's own self resetting fuse
Reverse polarity protection
startup and shutdow controller
Delayed startup and shutdown (5 min and 25 min)

http://store.mp3car.com/DC_Powered_4..._p/adt-015.htm