We know there are two common types of chargers' input port - AC and USB. The charger with AC input port, is very convenient to use indoors just by connecting its own power cord to the wall outlet, no more extra adapter. As for the charger with USB input port, it's much easier to carry outside and can connect solar panels, power banks with USB cables and your phone adapter, which is more suitable for outdoors charging. So do you prefer charger with AC input port or USB input port? Or prefer a charger with both AC and USB port like XTAR X2/X4 extended version?