My inclination is that the FN Five-Seven 5.7x28mm pistol is mainly meant to be given to tank crews and such where even a submachine gun takes up to much space. It uses the same bullet as the P-90 submachine gun and i am not sure on this one but may be an official NATO round at the moment or is on its way to be. It launches its bullet at around 2100 fps so it has alot more range than the 9mm. Its advantage over the 9mm is that it can take down targets at much farther distances because of its higher muzzle velocity. I would not recommend getting one unless you are just getting it to play around with and if thats the case id get it. I think as of now they only offer FMJ military ammo for it so it has almost no self defense uses. The last gun show i went to, i saw a few for sale at around 900 bucks.