Atlanteans are greater in number, and every one of them have adapted to the intense pressure of the oceans depths. Due to this Aquaman can deflect bullet for christ sake!! how are the amazons gunnna hurt that?? The durability factor I think wins this. Even if the Amazons have super strength (which the atlanteans do too), they are not as durable and therefore will have more deaths. Plus the atlanteans who can make it back to water will heal faster. this is no contest.