Artillery Cannon is a dangerous weapon in bases. Not only is the grenade damage high, the grenade and explosion may add up damage, dealing lots of damage. The artillery cannon has decent rate of fire for an explosion weapon. It makes an excellent support weapon and attack enemies in crowded areas. You are also good at taking down doors and repelling the door blockers.
The extra 7 ec can make a big difference when you start basing with your new EC weapon.