You can only pick one of these if we're talking about Single Player. I'm not the best player and thus I finish slower, but I've realized whether I win on Prince or Immortal the end plays out exactly the same and around the same time with the variance depending on what happened early game. For me to play faster is simply an issue of my ability to pursue victory and the AI has literally no impact on it past the midway point. Basically it just turns into Solitaire and certainly the AI's inability to achieve victory even when it has the advantage or its complete inability to even participate in late game systems at all is a huge problem. If the AI could start abusing air units, I assure you the late game could be a lot more interesting because right now, you can win nearly any war with 3 bombers and Civil Defenses.