As Byleth is the player-insert I don’t want to compare them to everyone else. I will say F!Byleth is the far superior version, if only for her tights.
Their support conversations are also pretty unequal but I didn’t dig through enough of them to have that be the basis of an opinion.
Mercedes is soft and lovely and just…sort of exists in comparison to her friends. She’s fine? She’s fine. I even married her as she is one of the gay options for a F!Byleth, and it was again, soft and lovely but unremarkable. Her family drama is interesting but doesn’t impact the plot enough to really merit changing her ranking. She is the best healer in the game though — good learned spells and heals herself when she uses them.
Lorenz is one of those “seems like a jerk but is redeemable” students, but of those I found him the most obnoxious/least redeemable of them. More dynamism and growth than Mercedes though. I just…never liked talking to him and they gave him the most punchable face in Fódlan.
A controversial pick to put this low on the list, but I just didn’t really relate to Marianne. She’s sweet but she’s just so…forcibly sheltered Church girl and I wasn’t about that. She’s also a little blinded by faith and this masochistic concept of unforgivable sin that is very Catholic and very much not what I’m about. Damn good healer though, second only to Mercedes.
Fun, inoffensive, not as much as people higher up. As I’m editing this I can’t even really recall any strong feelings about her during the game, so this far down she stays.