You’re talking aesthetic choices and that’s imo just up to aesthetic taste and little else. Tosen is more fleshed out, so he is better in that way, but Tosen’s blackness doesnt play any part to his character. It doesnt make Tosen better, or worse, nor should Tosen be criticized for it.
One dont need to “act black” as you think I was implying. Brother Onyankopon doesn’t act black. He dresses in Marleyan clothes, speaks Marleyan, served in Marleyan Army (Marley is the equivalent to Europe in ShingekiVerse) and he was, in everything but skin color, a Marleyan.
BUT, the reason why Onyankopon is imo more black than Tosen, is because ppl around him, and Onyankopon hisself, do acknowledge his blackness, even it it’s never mentioned again. He had to one time explain WHY he black (Sasha asked him straight up why he black)
Das all it takes, really. If the society in which our black character find themself in is essentially “color-blind” then being black dont matter. It’s like choosing gender in a game that never checks your gender for anything.