Should I get Civ 4 instead of 5?

I have Civilization 5 on my laptop. It's a really awesome game, but it lags like crazy after a while (even with all the graphics and stuff on low). I really enjoy the civilization games, but Civ 5 is getting annoying because of the lag. If I get Civ 4 will it lag less on my laptop? Should I even get Civ 4, or will it be a disappointment after playing 5?