Even if I could have the chance to save the Crazy marine before he lost it I would still pick foehammer given piloting skills are rarer than abilities required from ground troops.
There is tragedy in both cases, one witnesses his squadmates being basically ripped open to fit the infection form in and turned into hostile monster and left hiding alone in the middle of all that, surrounded by reanimated corpses of both allies and disposed enemies alike with the images burned into his mind.
Other gets shot down, burning into the ground where she could have died of various things like shock, impact force, explosion, burning in the wreckage and so forth. Both are undesirable and horrid ends but in this case it's choose one or the other to save.
I would think Crazy marine could have more horrid situation on his hands but it's the simple cold calculation that which one would be more useful in the long run in effort to better the chances of humanitys survival and minimalizing the chances of such horrid ends happening to others. So in this case, even though individual suffering (both mental and physical) are saddening, it would be second to minimalizing others from likely suffering similar conditions.