The answer: vastly different. And that’s just pointing out the obvious. The main focal point of the plot is the same – Cap wants superheroes to fight unregulated, Tony wants them to fight for the law as opposed to around it – but the battle between them is way, way larger in the comic, and the tactics get a lot more dirty. (Warning: spoilers ahead.)
First off, the main big difference: Bucky has nothing to do with the comic. It’s not a surprise that he has a lot to do with the third Captain America movie because, well, it is meant to be a sequel to the previous films in the series. This is probably the main reason why it came as a surprise to me that they decided to make the third instalment titled Civil War; it meant there was going to be a lot less focus on the title hero than what we’re used to in solo films, and I was intrigued to see how they’d make Civil War work without some of the big characters in the MCU – like the absence of the Fantastic Four. But, I generally really liked how they made it work in the end. It was a good balance between solo film and big superhero extravaganza, and the way they linked Bucky’s story in with the rest of the plot was very cleverly done, particularly with the further progression into Tony’s back story, too.
With this film being the first introduction of Tom Holland as the brand new Spider-Man, we weren’t going to get the big public revelation of Peter Parker’s secret identity in Civil War. That’s definitely a major advantage to Tony’s side with that action, as Peter is a hero known for closely guarding his true identity, so by getting him to make such an announcement allows Tony to paint Cap’s rebellion as unnecessary, and portray him and his team as extremists. But, this backfires on him later when Peter decides to switch sides and join Team Cap instead when he feels like Tony becomes far too extreme in his decisions.
One of the choices Team Iron Man makes is to clone Thor, who then kills a member of Cap’s team, leading to Spider-Man (and others) to then join the opposition. Things get a hell of a lot more violent in the comic, and Tony is arguably a lot more open to corruption amongst his ranks than Cap is, hence why he’s happy for the cloning of a God to occur, imprison rebel heroes in the Negative Zone Prison, and add super villains to his team in order to boost their numbers. Tony’s decisions are presented less abominable in the film and far more reasonable, which balances out the moral ground for the two leaders, making it more difficult to decide who is ‘good’ and who is ‘bad’ – this isn’t to say that the comic sets things out in a more black-and-white way, as the arguments on either team are set out in (mostly) the same way as they are in the movie, but the tactics Tony resorts too make him a lot less likeable, causing more of an internal conflict for those characters (and audience members) who settle for Team Iron Man.
The catalyst of the dispute in the comic is dissimilar to the one in the film. In the movie, we see Scarlet Witch lose control of her abilities, leading to an explosion killing innocent civilians. In the comic, however, a reality TV show (in which the New Warriors film their lives as superheroes for the public’s entertainment) attempt to raid the safe house of recently escaped super villains for the purpose of boosting their ratings. This fails miserably, which also leads to an explosion that kills civilians, but on a slightly larger scale than we see in the film. This cause I personally feel sways the argument in Tony’s favour a bit more, as the deaths are as a result of unregulated super-powered beings trying to fight outside their comfort zone for the sake of entertainment, whereas the mistake we see in the film on Scarlet Witch’s behalf perhaps, once again, balances out the moral ground between the teams, as battles between superheroes and highly advanced criminals are (arguably) inevitably going to lead to some sort of collateral damage. Yes, Wanda probably does need to learn to have better control over her abilities if her mistake has caused the death of civilians, but in the end, her intentions were to save the people ans avoid any casualties – if she hadn’t of intervened, the situation could have been far worse. Because of the absence of this in the comic, it makes it a little more troublesome for readers to join Cap’s team, as in the beginning I feel it’s easier to understand Tony’s reasoning behind his argument than it is Cap’s.
There’s a lot more differences amongst the comic and the film, small and large, but to keep spoilers to a minimal and still leave the book with some mystery and surprises, not everything’s been mentioned. To see this story added into the MCU was a fascinating choice, and although there possibly was an opportunity to leave this story to a bit later into the MCU and then briefly introduce some of the Netflix Marvel characters into the more mainstream part of the franchise, I believe that Civil War was a highly enjoyabe film that I personally view as fantastically executed, and appeared quite a contrast to the originally quite jovial First Avenger. It certainly showed a slightly darker route for the beginning of phase three of the MCU, and definitely leaves us wondering how the future of the franchise will pan out in the next few years, and exactly how serious the following films will become.