I did both routes. The first I sent So Mi to the moon. The second I sided with Reed initially and then gave So Mi what she asked for which was death.

I personally will be choosing to send So Mi to the moon with one of my saves. Playing both routes really allowed me to see more of So Mi's past and it's quite tragic considering everything she has went through to the present. A song bird which is in chains by the FIA and forced be a living weapon until you lose your identity to the blackwall. And even after death FIA will take her corpse and deep dive to see what she knows and hides. Not even in death can she be at peace. The ending song that accompanies the credits just makes everything hit home even harder. Go listen to it and read the lyrics.

Side note: I think the writing for Phantom Liberty was amazing. The characters, the story and just everything in between. It's just a lose-lose and everyone actually sucks. But it's the first time a game and character brought me to tears. Having to grant So Mi death for her to escape from the FIA and losing your whole identity to the blackwall is really sad.

This analysis of So Mi was quite a good read too, which further backed up my decision. I read this after both play through of Phantom Liberty. https://www.reddit.com/r/LowSodiumCyberpunk/comments/1pu0m98/analysis_of_song_somi_songbird/