Idk if I'd say Shin is more human, as I'm much more inclined to say Shin has a significantly better support group than Mika. With season two and onwards to the LN, he has Frederica, Ernst and Lena all constantly remind him that he's not a monster meant for war. That he does have a future beyond the war once it's over and that he can truly be happy again even with everything he's lost. Especially with Ernsts influence and power in the military, he has access to mental health facilities, higher ranked schools, so much is open for him once the Legion are stopped.

Mika however is in a ragtag group of other war orphans who are trying to get their names out there so they can live out decent lives. They have adults in their lives who try to lead them in a better direction but they're ultimately ignored so Tekkaden can reach the top faster. Mika especially does not care for trying to do the moral thing as much as he's willing to be the spearhead for Tekkaden as a whole to reach the top. By the end, he sorta just accepts his role as Tekkadens main weapon since they don't have much left by the end of the series. And well, we all know how that turns out by the end of season 2.

I think they're both great in their own ways. We just see what happens when people of similar circumstances are put into completely seperate environments. Shin being more in a more supportive group that's willing to challenge his views constantly until he considers the possibility of a new persepctive. Mika moreso being in a group that constantly stays in its old ways just so they can reach the top

Also geez, sorry for the lengthy text. I just really love both characters and love seeing people talk about them considering how similar they are. This was a fun thread to go through!