Longer charging time from PC

because the wall charger has more power.... i think if you look at the charger . it says 1amp or something... PC has half of that from USB
 
I wrote up a little something about chargers. Used Cell phones, Refurbished Cell Phones, and No Contract Cell phones from Falken Mobile — Micro USB Chargers
Its pretty much what the others have said. The USB port on a computer is usually putting out half of the power as the stock wall chargers. 1 amp verses 500mAh, or half the power. Half the power is double the time.

EDIT Dont let the title of the link fool you, i only put the link to the small write up i did about chargers, not trying to sell anybody a phone. LOL