I think the ArmA engine certainly gives you more control over your AI than the other games you mentioned.
The trick is finding the unpredictabilities (is that a real word?) and working with or around them.
There are alot of posts and tutorials on AI and mods which improve some aspects.
For example I use the zp_at fix mod and have it signed on our server as I hate the fact that the ai will use their longest range weapon to engage far enemies which is usually the AT launcher.
This of course waste that vital resource unecessarily.
Up to now it seems to work.
There are many other little tweaks around like this to customise the game to your requirements.
Dont think any other game has this expandability.