Comparing and contrasting OneShot and SOMA
 
1. Disbelief about the player's state
In both games, the player characters experience some kind of "disbelief" about
their state. In SOMA, Simon refuses to believe that he is a robot. At the start
of the "actual" game (waking up in Pathos II), the personality construct that
Simon was existing under just assumed he retained his old arms. When he made
it to the communication center, and experienced being crushed by a massive 
amount of water bought upon by a failed glass-dome roof, he had a "realization"
that he could breathe. A few seconds later, his arms flicker in digital noise
before revealing their true construction -- a diving suit. At two more points
throughout the game, the player can choose to have Simon look at himself in a
mirror. When Simon gazes upon his reflection in the mirror, he sees his true
form: a diving suit with a personality-simulating device stuck in the helmet,
haphazardly connected to the dead body in the suit with some nanotechnology
gel. In the case of OneShot, Niko repeadely states throughout the game that
they are not a cat. When the player arrives to the ground portion of the
Refuge, a robot (called Kelvin) can be talked to. Kelvin will remark that 
Niko is a cat, and should probably just sit and sleep with him, amongst the 
warmth that he emits. There are a few other cases where this occurs, at least
one on every map. Several characters will assume that Niko is some kind of cat,
or even be disappointed that a cat has been assigned to save their
compartmentalized universe. Despite opposition from themselves and other 
characters, both Simon and Niko go on to fulfill their quests.
 
2. Robot sentience and sapience
By far, the most telling comparasion between the two games is the regard to
sapient machines. In SOMA, there are several notable instances of sapient
robots (the most notable being Catherine), or robot-like creatures. Yes, SOMA
has "robots" that can't directly move around -- Catherine is another good
example of this. Throughout the game, she is at the mercy of Simon to carry
her around. There are also plenty of other robots in the game that are sapient
but trapped in unfortunate circumstances. Towards the start of the game, the
player has to re-energize some equipment, but ends up electrocuting a sapient
robot. If you talk to the robot, it will find it strange that you (the player)
do not see it as a human, despite many attempts to convince you otherwise.
It should also be noted that "robot sentience" is applied to many things in
SOMA that do not really map well to the human analogue. For instance, about
halfway through the game, it is revealed that a boat has somehow gained
sentience. Of course, all of these "haphazard creations of life" are bought
about by the WAU, the villain of the game. The WAU decided to, upon detecting
the impact of the asteroid, preserve human experience at all costs. This, of
course, meant applying humanity's existence to poorly-constructed and 
poorly-suited machines. This does not really parallel well in OneShot, but 
some things can be compared. The most obvious comparasion is that of Silver
and Dr. Kip. Silver, being a machine clone of Kip, "gained too much free will"
and left Kip to go inhabit the Barrens. Of course, to have sentience, you
must also not have sentience. Both games feature a variety of creatures, both
human and machine, that are not sentient. In OneShot, it is the concept of the
non-tamed robots that fills this requirement. OneShot uses the adjective 
"tamed" to describe if a robot is sentient or not. In the game, it is mentioned
that human personality principles must be impressed upon a robot for it to be
"tamed." In SOMA, the analogue of un-tamed robots would be the variety of
grotesque creations produced by the WAU. They do not feature sapience at all,
and, in fact, are unintelligent biological creatures.
 
3. Harsh endings
Both games feature notorious "good and bad" endings. SOMA actually features
two endings that both concurrently occur. In the first ending that plays out,
Simon finds himself trapped in Pathos II forever, as he did indeed place a 
copy of his personality onto the sattelite that him and Catherine launched.
He makes this realization that he is permanently trapped, and ends up
actually overwhelming the PDA that was running Catherine's personality 
construct, trapping him for an "extremely long time" and alone. The second
ending plays after, and it features both Simon and Catherine having made it
onto the ARK (the sattelite that they launched, loaded with computing
equipment that can simulate human personalities and experiences for centuries
to come), and they are both very happy with their state. The two manage to find
the rest of the Pathos II people in the simulation, and they can now carry on
their lives in a reality that was indistinguishable from the one from which
they came. In OneShot, there are also 2 endings, with similar effects. I am 
not going to discuss the Solstice ending, as it isn't as pertinent to this.
The first option for the ending involves Niko destroying the simulated
universe's sun, which would result in being ejected from the simulation. 
Of course, when this happens, the World Machine (in the same way that the WAU
would) aborts the simulation. If the player chooses to restore the sun to
its pedestal, Niko will become trapped in the simulation. Obviously, it might
be unwise to remain trapped in a simulation forever, but in true SOMA style,
you can do just that. It can be inferred that the two endings of OneShot are
mutally exclusive, unlike SOMA. In SOMA, both endings occur. In OneShot, only
one occurs under the gaze of the player. Of course, this does not rule out
a "retroactive destruction" of the simulated universe, where Niko later goes
to destroy the now-intact sun in order to be ejected from the simulation.
 
4. Ethics of human replication
By far, SOMA discusses this more than OneShot. At the start of the game, the 
player is replicated. This is first done when Simon goes to the doctor's
office, and has his brain scanned. The neurograph that was taken was used as a
"template" for build-your-own-AI systems of the future, so it is presumed that
Simon's consciousness was embedded into a whole variety of systems. When the
asteroid struck Earth, ending civilization above the water, the WAU discovered
these neurographs (along with 2 others), and implanted them into a personality
simulation device. That device was then embedded into a diving suit, whose
former occupant had experienced an unfortunate "explosion" of her head. About
halfway through the game, Simon clones himself again. Simon must actually go
and physically "kill" his earlier self, as he's still sitting in a chair. 
However, not much can really be done here. He must merely wait while the battery
dies. One can only imagine what sort of boredom the former copy had to endure.
In OneShot, it is heavily implied that the World Machine (not unlike SOMA's
Warden Unit) is responsible for duplicating consciousnesses of some external
beings, and re-mapping their bodies to be that of robots, human/feline
hybrids, or human/bird hybrids. Since all of the races featured in OneShot
exist only in the compartmentalized universe, it can be presumed that they are
duplicates. Niko found their way into the simulation somehow, but it is not
fully explored to the extent that it was in SOMA. Of course, within the
confines of the simulated universe, personality replication is clearly
happening (see the aforementioned situation with Silver).