I don't know what people are talking about, but CivIV runs great on my SR MacBook (X3100). Maybe its the 4GB of RAM, or the drivers I have for the X3100, but through bootcamp I'm able to play with almost all maxed settings on huge maps in epic games with very little lag.
I haven't really had issues with games on my Macbook yet, so I'd go for any of the Civs.
~Thursday