In a game some time back, I overlooked the vulnerability of a sizeable city and the AI took it. Lots of partisans appeared (a unit I don't normally build so have little experience with). They were all "none" units and I used them to pillage.
Boy were they tough to destroy! The havoc was most satisfactory.
A few games later I wasn't in democracy so when I decided to do some pillaging, partisans were the guys for me.
But the partisans I built dropped like flies. Not so satisfactory.
As far as I could remember the attacking AI units were of similar strength in each game so I started to speculate that partisans generated by enemy conquest have some inbuilt advantage - all vets, or something.
I have read of more than one tactic in which the player intentionally allows a city to be taken so I wonder whether anyone else has noticed this or knows the explanation?
By the way - another case of disparate combat results is definately barbs -v- human, barbs -v- AI. On the (rare) occasions that the barbs pick on the AI and not on me I am cheering the barbs on only to see some lowly AI warrior escape without a bruise when I know that my phalanx would have been creamed. I suppose the barb bonus in deity doesn't apply against the AI. Annoying that.