Yuichuro and Eren have many similarities between them. Likewise with the two series that they are from. That being said, Yuichiro is easily the better character at the moment. Granted, Seraph of the End is early on at the moment. Still, Yuichiro doesn’t take time to feel sorry for himself. He wants to destroy vampires and that’s exactly what he does. Right from the get go he takes a lot of them down. Eren was unable to do this until he got his Titan Form. Even in that mode, there’s no way Eren can take Yuichiro down. Yuichiro’s way too fast and has a berserk mode of his own that would overpower Eren. Yuichiro may have debuted later, but he is just a better character whose character development puts Eren’s to shame. Yuichiro wins.