AI in JTS games

[Ekaton]

I have several JTS games. I currently don’t have enough time to play against a human opponent with any consistency so I tried to play some larger scenarios against the AI. Here are some of my thoughts:

1) In CS Normandy ‘44 the AI is quite alright (Caen Country scenario at least). I took Bayeux and Caen on the second day and fortified my positions on the western side of the river. German counterattacks are done alright, a lot of tanks just east of the river, shooting my troops on the other side, causing heavy losses. Attacks against my paratroopers and commandos are a bit half-hearted but generally alright. AI doesn’t just send troops blindly to attack but rather created a consistent defensive line, only attacking in one area, concentrating its troops and support units there. Troops stick to their prepared positions and don’t counterattack when they are hopelessly outnumbered.
2) I gave the AI “a nudge” a few times, retreating its units from very exposed areas. I was afraid that this might break some scripts but I don’t think it did. 
3) I bought Moscow ‘41 yesterday and moved to the big one, operation Typhoon, the basic variant. A completely different experience. On turn one Soviet units left their trenches and counter attacked, suffering obscene losses as a result, not achieving anything in particular. I concentrated my forces in several schwerpunkte and that’s where the enemy suffered the worst losses counterattacking. 

Why is my experience with both games so different? They use the same engine, what makes the AI so awful in one game and rather decent in another? Is AI likely to be better in smaller scenarios? Is the AI better in newer games? Do you have a similar experience?