With many of the cars, you will be buying essentially the same car. The Miata's have different names, depending on what country the were sold in. (Eunos Roadster, Miata, MX-5, Roadster, MX-5 Miata.) So if you get one, and I'm just making this up, that is called Miata 2500 Supercharged NA, the MX-5 2500 Supercharged NA is pretty much the same vehicle. It's just a country designation. The Vitz is called a Yaris also. The Madza 110s is also known as a Cosmo Sport. There are quite a few like this in the game.
As Barra said, if you want to own one of each, the best thing to do is to buy everything that doesn't have a check mark next to it in the Used Car Dealership, the Online Car Dealership and the new Car Dealerships. You'll get them all eventually, but some of them show up very rarely, so check the UCD often.