good control

Everything works without fuss, controls are well labeled, and physical build quality is decent (mostly metal)

While I am unsure of what sort of PA system that only requires a $100-class mixer has a proper control room, it is a convenient feature to have two pairs of stereo outputs, and can eliminate the need for a distribution amplifier (costly) or Y-cable (inexpensive but degrades signal level and signal/noise ratio) on the output