Privilege and Control
Not that Captain America: Civil War hasn’t been dissected to death by now, but I think a major difference between Tony and Steve is privilege and control, and how that affects their choices. Obligatory “haven’t touched the comics” forewarning, this is purely based on the MCU movies. I also haven’t seen the movies in a year or two, so bear with my plot memory here.
Tony was born into money, fame, and privilege. He’s a rich, cishet, middle-aged, white man, the son of a rich, cishet, white family. He always has money, he always has security, and he always has freedom. Even in his own movies, when he’s put on house arrest by Fury and SHIELD, he’s got a ridiculously loose leash, sneaking out on joyrides and such.   When he’s under fire from the media, he’s allowed to play the part of a childish playboy, and his reputation isn’t overly damaged from it. Even when he causes damage, he uses his fame and fortune to cushion the blow, like buying buildings in the seconds before he throws Hulk into it to avoid the legal fallout.  Yes, this man built his own superhumanity, his tech and his weaponry from scratch, but he’s also coming from a position of privilege, wealth, and freedom that his allies and enemies don’t always have.    When he breaks rules, often it’s for his own gain and wants. He steals SHIELD files, defies and ignores authority and instruction, and is admittedly narcissistic and manipulative when it comes his plans for and treatment of his coworkers and allies, and the assertion that he can be and is the smartest person in a room. He rarely owns up to his mistakes and problems, often attempting to put the blame on someone else.
In comparison, Steve was born into poverty, disability, discrimination, and war. He was the disabled son of a widowed, immigrant(?), lower-class mother, and was regularly sick, hungry, and regularly bullied and attacked. (Yes, I know he started a fair few of those fights, but I’m willing to bet there was bullying and unprovoked harassment for his family and his extensive disabilities.)   He was suddenly elevated in health, strength, and status with the superserum experiment. He fully consented to the procedure; not all enhanced humans can say the same. He was born and raised in a time where racism, discrimination, and government control of freedom and autonomy were rampant. He spent the majority of his first movie battling a corrupt and fascist government organization.    He also breaks rules and often defies his superiors, yes, but typically, he does it with the safety of other (innocent) people in mind. Often, the contextual reason for his rebellion against authority is his presumption that the authority is putting other things before the safety of innocents. When reprimanded, he typically owns up to his actions (although he often reiterates the reason being the safety and protection of the innocent and helpless).
When Tony argues for the Accords and for loss of autonomy, he’s viewing it through the lens of his own freedoms and privilege. He’s used to being allowed to do what he wants, and assumes that the Accords is a positive change for him. His driving factor for the Accords is his guilt and trauma, and he also seems to assume that all the Avengers are like him, both in power, control, mindset, and privilege.    He expects, and gets, a far looser leash than any other superhuman does. Registering his true identity isn’t a problem for him, because he’s been proudly carrying the title of “Tony Stark, the Iron Man” ever since the first Iron Man movie. Registering the full limits of his technology isn’t a problem for him, because he can always take off the suit, or put on another suit with smarter tech and bigger guns. Giving up his freedom and bodily autonomy to a corrupt government organization isn’t a problem for him, because he can and does do exactly what he pleases, regardless of who he claims to be working for.    He doesn’t even suffer for other superhumans using his technology against the Accords (e.g Spiderman), unlike Hank and Hope Pym, who are forced to run and go underground after Ant-Man steals their technology during CA:CW.
When Steve argues against the Accords and for personal autonomy, he’s viewing it through the lens of his own struggles against authoritarian control and loss of freedom. He’s used to being undermined and micromanaged, used as a showpiece and a weapon instead of a human being with opinions and autonomy. He’s well used to a time period when people are criminalized for birthrights and appearances they can’t control, and are forced to register themselves to higher authorities.    Based on all this, he assumes that the Accords are a negative change for himself and the Avengers. Registering his true identity isn’t necessarily a problem for him alone due to his status as a revenant war hero, but he knows the invasive damage it can cause others. Registering the complete measures of his abilities is like requiring normal humans to state how much they can lift or how fast they can run; it’s also a violation of an enhanced human’s privacy and autonomy. Steve can’t simply turn off his powers; he’s always going to be stronger and faster than other humans. He knows that giving up his freedom and bodily autonomy to government organizations he knows to be corrupt and not necessarily trustworthy (see: the launch of a nuclear missile on a major American city still packed full of trapped and innocent civilians; the long-time infiltration of a fascist organization in a supposedly secure government body) is a slippery slope to a familiar government state of profiling and oppression.
To summarize, I think the stances each man takes is due to his privilege, or lack of it, and his power, or lack of it. Tony comes from a position of privilege, and this colors his decisions. Steve was born with and raised in a time with little privilege for many people, and this colors his decisions.
