The USB charger is handy here at the desk. It can be tucked away around the computer when not in use. It takes up less space in or out of use. It is my usual choice for my occasional charges. It also works with the cigarette lighter adaptor in the car. However the wall charger has it's place as well. It is useful when access to a computer is not handy.
There you go. The USB gets used more but I wouldn't want to be without wall charger.