[orthoxerox]

SMAC had a few restrictions that made dealing with its leaders harder, but more realistic. In Civ 4 and later Civs you can build complex deals and propose them to the AI leaders. If they are bad, they tell you they are not acceptable and you can try again and again. You can see the "diplomatic price" of each item.

In SMAC you could make a single proposal per turn. If it was good, they would accept it, if it was almost good, they would counter your offer, if it wasn't good enough, they would actually get madder at you and stop talking for the rest of the turn (or for a few turns if you relations were that bad). That was the only feedback you'd get.

This small change made parlaying with AI leaders feel more realistic. Instead of going "Hm, you won't give me Zaragoza and all your money, because 'we are losing' is only at +15, I'll come next turn when it should be at +17" you start building a mental model of each leader and proposing deals you think they should accept.