Ok to start off with this not a theory post and no new information on who Superior will be has been provided to me this is just my opinion on why O'Hara should be Spider-man.
He's not all that different from Peter:
It may seem like an odd thing to say but his attitude and even how he looks physically are quite close to Peter's. Now you may wonder why this matters and in truth it shouldn't but for the most part people have trouble with drastic change. Miguel is similar in physical features enough for most people to swallow the change. Of course this is entirely dependent on artistic interpretation but all the basic features are there. Similar face, similar height, similar hair etc.... Even if we leave the physical side behind his morals aren't that different from Peter's. Yes he has a tendency to be impulsive and slightly less forgiving to his enemies but what we have to take into consideration is that Miguel had no heroic motivation to become Spider-man. He was the victim of Tyler Stone so vengeance was his main motivation. To me Miguel is how Peter was just before catching his Uncle's killer. Angry, impulsive and even a little cocky at times. With no good old Uncle for Miguel to aspire too he has a tendency to react without thinking and this has left quite a few of his villains badly injured or sometimes dead but would Peter Parker have been any different had he not had his Uncle to base his morals from? Probably not. Without his Uncle and with all that power Peter most likely would have gone on to badly injure and kill a few of his enemies by accident.
Despite this Miguel is not malicious and shows shock and even horror at what he does on occasion. For the most part he is a good guy but just has some anger issues. If you needed further proof that he isn't as bad as he comes across he was able to lift Thor's Mjolnir so i'm pretty sure that's a good qualification!
Miguel is also a very gifted geneticist so we would not lose the scientific side from Spider-man. Another interesting thing is that over the course of the 2099-verse Miguel was introduced to the "With great power comes great responsibility" line so even though he doesn't take it as seriously as Peter if Miguel were to replace him we wouldn't lose that famous quote from the Spider-man mythos and it gives Miguel a chance to grow and develop on this basis.
One thing that has people worried is that they think they will lose the old Spider-man who made quips during his fights and while Miguel is often portrayed as the strong silent type he does have a sense of humor so it wouldn't be hard to push this into his personality a bit more.
How he is different to Peter:
Despite the similarities Miguel is his own character and I have never thought of him as Peter Parker 2.0. Peter is always portrayed (sometimes wrongly) as a kid in adults clothing. Miguel certainly is not. His view on the world is slightly larger than Peter's as at one point he became the head of Alchemax's research and development department so he tends to see things in a more serious business-like quality. This is something Peter has never had the opportunity to do. Although he recently got a job at Horizon Labs that still pales in comparison to being head of one of the biggest genetics companies in the 2099-verse. So to put it bluntly he is more of an adult than Peter is but then again perhaps Peter could be if the writers actually gave him a chance.
Although Miguel doesn't intentionally kill in random encounters with his rogues there have been instances where he has gone in completely prepared to kill. This is something Peter no matter the circumstances would ever do. If Peter gets pushed too far he tends to snap and generally beat the hell out of anything that gets in his way. Miguel on the other hand becomes cold, calculating and ruthless applying that scientific mind to slightly less amiable actions. Suffice to say if Miguel were to take over he would approach Peter's villains a lot differently than Pete did and would adopt a more predator hunting its prey attitude to the whole thing.
Peter has a tendency to be quite reserved and sometimes shy (out of the costume that is) where as Miguel is the opposite he seems to say what he's thinking no matter the circumstances which has in the past landed him in hot water (in and out of the costume) by telling people exactly what he thinks of them. This could create some very interesting dialogue with Peter's supporting cast, especially in the Avengers where Spider-man is basically seen but not heard (unless the writer decides to throw in a joke). If Miguel were to become the new Spider-man then he would make his presence known on the Avengers and would tell them bluntly if he thought their idea was stupid which could put him on edge with a few members of the team leading to some interesting side-stories.
Miguel unlike Peter is also at near constant risk from exposure due to his powers. Peter's powers are quite subtle and can be hidden well when out of the costume. Miguel's on the other hand are not. For one he has claws protruding from his hands and feet (which he uses to scale walls) meaning normal everyday things can be a challenge. Unlike Wolverine's these claws are not retractable. Miguel can flatten them against his fingers to make them less noticeable but he cannot hide them entirely. Meaning that if he doesn't concentrate he could end up slicing through nearly anything he touches. He also has elongated canine teeth (essentially fangs) that can inject venom through a bite. These will be hard to hide from people who take a good look at him.
If that wasn't hard enough to hide Miguel also has another problem. Instead of the good old spider-sense Miguel has enhanced senses. These are very effective and have in the past allowed Miguel to hear a gunshot, pinpoint exactly where it was fired from and avoid getting hit at the same time. These senses come at a cost however, due to his enhanced vision Miguel's eyes are bright red. This means that Miguel in the 616-verse he would have to either wear glasses or invent some very big contact lenses!
Miguel in my opinion has proven that he can be Spider-man and not just a Peter Parker knock-off. His morals and attitude while not a million miles away from Peter's are different but not different to the extent that we would lose the Spider-man we all know and love. He would still be scientifically gifted, funny (to a certain extent) and a good guy at heart except with all of Miguel's qualities thrown in. the fact that his powers are so pronounced also means that hiding his identity will be a very big task so a lot of stories could divulged from this very problem. I personally would love it if Miguel became the new Spider-man and hey if you don't like him its not like Peter Parker will be gone for good. This is Marvel after all.