I play them both, and love them both. They're both strategy, but they're both VERY different kinds of strategy...
Abraxis, thanks for your comparison of the two games. It's posts like yours that really help those of us who are considering other software. I confess I hadn't even heard of the other game and will have to check it out.
I sure don't need more immersion. Civ puts me into another time dimension where hours go by like minutes. I was up until 4:30am three times this week...but I won! Then I resolve to get my life back only to find, about a day later, myself getting the itch to play, because each game is a new situation. Fortunately, I'm retired, or I'd have to uninstall Civ.