I've played SMAC for about 2 years (my best game is diplomatic in 180 turns), and i've played civ3 only 2 times(warlord and regent), and i'll give a simple comparison:
Civ3's ai is much better than SMAC's AI?
not really, the only improvent is that ai has improved in expansion, and knows how to attack in mass and thats about it. Oh, and i FELT like the ai had about 20% production, tech, growth, advantage in regent (SMAC had that much advantage in the 2nd hardest level) level.
And finally in Civ3's AI r uselessly ruthless. In SMAC even Hive would give an reasonable answer (if im as powerful as him) when i refuse his offer, but in Civ3 the ai gets mad without any reason (in SMAC at least u know why ur enemy faction got mad : u did not choose their social ruling preference) because i did not accept their unfair deal. Afterward they join together (i NEVER start a war) to gang up against me.
There was much more ways to win in SMAC and hardly no single methods was better way to win than the other. In Civ3 u have to start aggresive in the beggining in order to survive. If u dont follow what i just stated above u will be likely to lose. Strangely in Civ3 the units have 3-5 hits: the result is a unit with 2 defence has a good chance to win against a attacker with 4 attack......something which was fixed back at Civ2.......
In Smac there was stuff that were very original (unit design, social engi, using psi units, artillery units [i hoped archer was like that

]).
Yes, there was flaws in SMAC (such as redesigning all units every 3 techs) but compared to Civ 3 its nothing: culture, while an interesting concept, it can be quite weird sometimes: my units conquered a city, but after only 1 turn they becomes cityzens of the conquered nation because of its advanced culture........what a joke........(note that is so unrealistic), with luck some of ur elite units can be promoted to a GL......u just got a free wonder!
Believe me folks, Aok has more strategy than this...