Least favorite part (spoilers)

[Abion47]

Could you imagine Catherine's reaction would be to Simon deciding not to launch the ARK?

Now that I think about it, though, that could potentially be a really interesting way to end the game. Simon finds out (or finally puts two and two together) before the launch that he himself wouldn't end up on the ARK and that he's doomed to remain in Pathos-II for the rest of his artificial life. At that point, the player can choose to launch the ARK or not.

If you don't launch the ARK, Simon and Catherine get into a huge fight that ends up with Catherine overloading, possibly after trying to forcibly take over Simon's body and do it herself. Afterward, you have the second chance to launch the ARK, but it's too late. Catherine is gone forever, and you have to live with that guilt.

If you do launch the ARK, Simon and Catherine have one last philosophical discussion which ends in a final choice - return to Tau, climb the barrel, or sit in Phi and pull your battery. Depending on your choice, there are another couple of philosophical lines of dialogue, and the game fades to black.

The after credits scene could also potentially change. It would be pretty much the same if the ARK gets launched, obviously, but if it doesn't get launched, what would it show? An ARK devoid of life? An ARK breaking down? Just a deep black limbo with literally nothing at all? Depending on how the final sequences play out, Simon might not even be there, and instead, you're playing the failing ARK scene through the eyes of the original Catherine, wondering how it all went wrong.

This could potentially be an even more powerful ending than the already powerful ending of SOMA. And now that I've thought about it, I'm a little sad that we don't see those possibilities of choice.