They are both about twin brothers that take each other's places. In Your Honor, Suho works as a judge and Kangho's been to jail 5 times. In Sirius, Shinwoo works as a Chief Detective and Eunchang just got out of jail. They have very similar plots.
Both dramas are action dramas about the police. The difference between the two is that in Athena: Goddess of War, it's talking about secret agents while Poseidon is about the police.