SORRY IF I RAMBLE, I KINDA JUST TYPE WHAT I THINK.
Kill Trevor because he is unstable.
Kill Michael because he pissed me off.
These are the two choices you are lightly placed into right after completing the final heist, and both options should never be picked, because I believe the "Death Wish" Mission is canon because of the survival of all three characters. So why bother killing off one of your characters if you can save all of them? to save time? No. Because rockstar wanted you to realize who was the main antagonist of the group in a "What If" scenario.
Trevors Death: So far, we see trevor as a "Psycotic, unstable, Woman-whoring man" but he is much more than that. Trevor doesn't kill when necessary, when it doesn't interfere with his life. Sparing that one man in the beginning of the game is enough to show you that Trevor does have a concious, and doesnt just kill randomly, even going so far to act as an older brother to wade, even if he kills those who he finds a threat to him. Trevor loves women and respects them, going angry when people say MotherF***** and even promises to kill Madrazo if he hurts his wife. Due to childhood abuse, it is what shaped Trevor, because in the mission Mrs.Phillips, immediately trevor beckons to every call of his mother, and seems to be brainwashed into obeying her because he just wants approval. Trevor is a nice guy, and trevor even believes he is the most "Sane" out of the group because of his carefree lifestyle, something he is proud of just because it defies everything America stands for.
Trevor is the reason I believe ending A is the worst ending. He comes to franklin happy, expecting the best of his buddy, only to be destroyed when Franklin says he has to clip him, calling him "Judas" because of his betrayal. Trevor did not expect to be betrayed again. Trevor thought better of franklin and believed he was a genuinley honest guy. Trevor handles the situation widly, and doesnt even fight back, doesnt shoot back, just tries to run away until michael hits him and gets into his predicament. I believe after that incident, where his best friends betray him, is when he gives up and asks to be shot. Trevor is the "Hero" of this game.
The whole game Michael is concieted, thinking about himself and how he can make his family love him, and it just seems like he believes he is doing what he is doing for good. Michael seems openly like a nice, charismatic person towards fraklin, mentoring him and teaching him how to move on up but that is because Martin Mandrazo requires him to pay 2,500,000 on a redo of his house, a house that Michael destroyed. Michael continues to sublty try to be the center of the game, even taking Trevors score because he didn't want to live like that, because he had his movie he wanted to work on. It just seems that michael is very egotistical and just tries to focus on his needs first and others second. even acting bewildered when franklin calls him to clip him stating things like "You're gonna clip me?" while saying things like " I was a father to you!"
Michael eventually becomes more agressive towards franklin, shooting at him while franklin is chasing at him and instead of taking his own advice like a hippocrite, he decides to fight, even though franklin is explaining that it is to survive, and "this is what you taught me." kinda stuff.
Franklin in ending 'B' explains that they just used each other meaning franklin thought all along that their partnership was a hoax and it's michaels fault for tricking himself that it was anything more for personal greed. Michael is stubborn, and even if you (try to) help michael up, he gets the last laugh by headbutting you before falling to his death. Michael reveals to be more centered on himself in this ending but hurt at the same time because franklin would do such a thing. This ending Franklin reveals to be more of a villain than michael, doing it just because Devin Weston told him to.
The thing about Michael is his attitude in ending 'A' where michael helps Franklin kill trevor, (trevor does not in ending 'B') and even laughs at trevor in his death, confirming that Michael was more deranged than Trevor, killing Trevor his best friend just because Michael was afraid that it would happen to him if he and Franklin didn't do it. Michael in this ending seems to distance himself from franklin after this ending and they go their own ways, even though in ending 'B', Michael seems more close to Franklin and even invites him to Dinner.
SUMMARY INCASE I WAS CONFUSING:
Trevor is the hero of the game. Trevor represents "True" America. Trevor has high expectations for his friends, Trevor even goes so far to forgive michael in ending 'C', showing he isnt as deragned as everyone had thought.
Franklin is the Morality of this game, Doing things to support yourself 'B', but also helping others when in need 'C', or taking matters as an act of justice 'a'
Michael is the Greed of America. Doing things for himself 'A', and even being a hippocrite when explained by franklin that he needs to survive and that michael told him he knew when the time would come and that was the time 'B'. Seems to really care about friends and family (Minus Trevor) but needed to fill the void in his life before he could worry about himself.
I believe Michael is the true antagonist of this game, but is pushed to that conclusion very silently, as michael appears in all 3 endings, either as a psycopath, or a frantic hippocrite, or even as the front of attention again just like in ending C.
i don't know, just my opinion.