This question is aimed at Terminator 2: Dia do Julgamento. Would one think that he was weighing the decision that "It is either that this T-800 could end up going rogue" or "It is worth a shot or else I would have to send a human back again and this time another Terminator (what we come to find is the T-1000) would be way too advanced for a human to fight."
Is there any explanation in sources (particularly the novel or from James Cameron) on why John would risk doing this?
Os filmes novelização oficial gives us the only answer that could possibly suffice. John Connor sent the T-800 back in time to protect his younger self...because he remembered being rescued by one when he was his younger self.
They passed numerous galleries filled with hulking machines, now cold and motionless; a vast library of strategic technology Skynet had designed and built. Even John’s vaunted techs would need years to study it all. And once having deciphered the machines’ functions, John would have to decide whether to destroy them, or trust that the new society rising up from the ashes could use them responsibly.
He had no information to guide him in this, no memories of the past resonating with his future. On what happens after today, John didn’t have a clue. But as he walked up to a massive steel door, the memories of the past flooded into his present. John knew he was looking at the door of fate. He knew that behind it he would find what he was looking for: the final answer to the question that had haunted him all his life. Was all of it true? Even to the last?
It's not clear if this is a stable time loop (in which case, there doesn't need to be an original causation) or whether the earlier (later?) John had a different motivation.
No Terminator: The Sarah Connor Chronicles episode "Today is the Day (part 2)", young John Connor answers this question in a speech he makes to Jesse.
You know, I've been running from the machines my whole life. They tried to kill my mom before I was even born. When I was twelve they sent one after me. I was a kid. I was stupid. I didn't know what it was all about. Both times future me sent someone back to stop them. The first time it was a soldier. His name was Kyle Reese. And he died saving my mother's life. The second time it was a machine. I used to wonder why I did that, why I took that chance. I don't wonder anymore.
Human beings can't be replaced. They can't be rebuilt. They die and they never come back.
There is a third possibility: simple escalation.
As an adult having both grown up with Sarah's stories and having seen what the more advanced cyborgs could do as a child, John would have conhecido that leaving his past-self defenseless against an advanced future weapon would be both dangerous and foolhardy, and that his chances of survival would increase if he sent back some other type of weapon to even the playing field.
"Pops", the T-800 which became Sarah's protector, was simply one off the assembly line...and is a possible alternate universe version of the mesmo T-800 which would eventually have been sent back to protect John himself. So in truth, there are centenas ou talvez até milhares of T-800s with that particular face and body which could have been used. In the second movie, it was stated that that specific unit [we'll say "Pops" for clarification against the others] was "reprogrammed" to be used as a Protector.We have visto humans reprogram Skynet tech of various forms for their own use in Terminator: Salvação. As Kyle is still a teenager, it's clear that this point of the future is set às vezes before Kyle could father John, so it may simply be that they only had the programming tech necessary to hack an 800 model or below. By the time the T-1000 was deployed, the Resistance may not have been able yet to fully control a liquid metal nano-tech Terminator, but still needed to send alguns Terminator as a counter measure.
Again, this makes logical sense; sending a human back resulted in Sarah just barely surviving, so obviously something with a bit more power needed to be used. Without wrapping them in human flesh, sending weapons back is impossible, and they'd likely end up in the wrong hands. Sending back a thinking machine which could double as a guardian e a weapon, however, while also being somewhat of an exception to the rule is sensible.
There is another, also likely answer: simple availability.
In most of the future scenes shown in T2, the most numerous and commonly used combat Terminators de longe are the T-800; we see them stepping on skulls and massacring hordes of soldiers on a few occasions. Obviously, it was mass produced, so it's likely this is the unit the Resistance had the most opportunity to study to facilitate their reprogramming. From there, it was a simple matter of gaining a fully cyberized version [likely one mass produced with Pops' face], resetting the programming, and sending it out. In hindsight, it might have made more sense to send a T-1000 to defender against a T-1000, but in that film it was stated to be a "new model", so it was either rare at that point, or they hadn't deciphered how to reprogram one yet.
If that was the case, John simply would have gone with what was available.
Todas subseqüente appearances of Pops, however, would então be influenced by John's recordações of the specific model; even Pops himself alluded to it being "a face John would trust" in the second film. And in the third film, they were banking on John recognizing his former protector and thus trusting him/it more off the bat. I can't speak to how the latest films may alter that continuity.