But however if they manage to do a pincer movement you will be dead and waste all the resources
Again, assuming you've left your flanks open and failed to brace, we can continue this back and forth hyperbole all day long, each have advantages and disadvantages.
Bofors - Ruins multiple squads in seconds, take focus for the enemy to kill or completely locks down a section(s) of the map until late game leaving you to focus on harassing them, it outranges pak's and mortars (unvetted) with it's barrage.
AEC - Can move and isn't stationary, kills models near 70% of the time it shoots.
But, the AEC can be killed in 3 fausts, can be one shot by a mine, requires focus and micro to be effective and comes near useless late game.
Bofors causes the enemy to ignore it until late game by which time you can protect it with tanks or focus a lot of effort into killing it when it's built.
When the enemy has 15,000 squads swarming you, I know where I would rather focus on one side and feel relatively safe on a flank than trying to path an AEC around the sqarm of OST