It has a long stun (0.5 secondes) and very high damage (up to 54 damage). It can both murder herds of unarmored titans and put a significient dent into lightly armored titans because of the high base damage of the pellets.
Like the spreader cannon, it launches 7 small projectiles in a cone, so usually this turret will not achieve its full damage potential against lone target. However, it is much more likely to hit moving targets.
Assault Cannon turrets are significantly bigger than the regular turrets, making them harder to place.