I have been playing Capitalism II for many years now, just replaying it over and over because you have so much paths to choose. So I came lurking at Capitalism and saw in a review that this one would be even better in the gameplay.
But I have to disagree. Capitalism has all the same gameplay, but it lacks the good interface from Capitalism II. This is a bit weird review because I'm comparing the sequel to it's predecessor. But it can help people to decide if they are in the same situation.
So should you buy it? If you can spare $6, buy it for the extra missions you get in this version. Low chance you will regret it. If you still are having fun in Capitalism II, just stick to that one for now.
If they would make a capitalism III with exactly the same gamplay again but with modern resolutions and upgraded sprites, I'd buy it in a heartbeat! That's just how much fun this game is.