Well they are both really good cars. The best thing about a civic is that they are very reliable. But they have very plain interiors. The mazda 3 is a little bit "nicer." I've ridden in one, but not driven one. The mazda will be a little safer in a crash. The worst part about a civic is that it seems like everybody has one...I don't like having the same car as everyone else. But it just comes down to which one you like the best, because they are both great cars.