I also thought they were simple devices until one evening, while charging my iPhone, original USB charger installed in wall decided to pop and smoke up the place. Quality of chip used to convert 12v to 5v can matter. $10 extra dollars = peace of mind...
You could go with a general aviation usd charger. Probably better but not cheaper then Amazon https://www.aircraftspruce.com/catalog/pspages/usb-adapter.phpYMMV
