That's one thing - the second is pure firepower - that system goes on the USAF CSAR Ospreys. Last time I checked, their missions were run by two aircrafts - in Pave Hawk example one was used as a transport ship, second as a backup/gunship. Both armed with TWO miniguns. Now with MV-22 the numeber of weapons is cut in half, and from that, only one can be used after one lands to get the SF guys on board.
No matter what gizmos you use, you can't cover as many sectors with one gun, as you could with 4 (6 with now-retired Pave Lows)