Which is better, photo flash or fill light?

Flash is a cold light source, which can be synchronized with the camera and is more convenient to carry. The disadvantage is that the power is limited and it is generally difficult to work continuously. Let the lights cool down about 20 times, or there will be a strike. Generally, a long bright lamp is used to supplement the lighting, but the color temperature of the lamp can not be well guaranteed, so it may turn yellow or affect the color of the main body. Generally, an external power supply is needed, which is not as convenient as flash.