Speaker arrays are designed to focus all frequencies in a desired direction. Drivers, cabinet and electronics achieve this at at a hefty price tag.
Arrays Can Reduce Opportunities for Feedback
Small arrays like sticks with bass bins are designed to cover 180 degrees horizontal. This works very well in highly reflective environments by allowing more coverage at a lower volume. Many stick systems claim no feedback, but this isn’t true. Arrays use multiple high-end drivers which eliminate having a single hot spot for feedback, but if you are using more than two mics, you have to be careful. All PA’s can be turned up enough to feedback through a vocal mic (usually most amplified and effects don’t help). Every additional mic lowers the threshold of feedback by -3dB SPL.
As long as you’re not trying to sound like Led Zepplin, they work very well for lower volume and fewer instruments.
Large arrays are what you see at most concerts. They have small angles of dispersion. Bass cabinets are designed to be directional too. Each cabinet of the array is aimed at a small group of seats, so volume can be set the same for all. You can be loud in a small area or carry multiple speakers.
Used correctly speaker arrays can’t be beat.