Buying A Cartridge Direct From Japan

Seems like there can be some decent savings when buying certain cartridges directly from Japan, vs buying from here in the US. Since I'm just learning about cartridges, would there be any kind of difference between a Japan model and a US model, maybe electrically or something, that would prevent using a Japan model here in the US? I would think they would be exactly the same, but I want to be sure before I maybe do anything. Thanks.