Generally, there is a tradeoff between resolution quality and minimum bandwidth requirements.
If the published mobile video stream is consumed by other mobile devices, VGA (640x480) is often adequate enough for smaller mobile screens. HD (1280x720), in most cases, is often unnecessary as mobile devices generally do not have the screen real estate to noticeably benefit from HD.
However, publishing lower resolutions from a mobile device might be an issue when viewing said stream from a desktop. Given that mobile devices often suffer from bandwidth limitations (versus desktops), you would need to find the acceptable balance point for your end-users between minimum resolution that is viable for the desktop viewing experience, and ensuring that the mobile device’s uplink is not congested due to high bitrates.