Aside from the fact that both VGA and QVGA are displays or screens for different devices, there are some differences between them, basically on their specifications. VGA is the short form of Video Graphics Array. It comes with a resolution of 640 x 480 pixels. Due to its size, it is very okay for desktop or computer-based applications. In terms of processing power, VGA consumes more, and that's why bigger sizes of VGA are equipped with enough processing power. However, the problem with VGA is that it is less acceptable to people.
QVGA, on the other hand, is the short form of Quarter Video Graphics Array. It comes with the resolution of 320 x 240 pixels, which is lower than that of VGA. QVGA is mostly used as screens for mobile devices, and it doesn't consume too much power, unlike VGA. QVGA is accessible and more acceptable compared to VGA