I'm actually reminded of the ending of The Social Network, when Zuckerberg's lawyers decide to settle out of court on the basis that even if Mark's assessment could eventually be argued in his favor, a jury would have been highly unsympathetic towards him.
At the end of the day, being correct or having the moral high ground doesn't excuse one from being a completely unlikable asshole. In the absence of evidence this is what completely undoes Chuck. That said I don't think anyone would just blindly let Jimmy walk away with anything. Kim is the only one other than Chuck who knows what he's done but the only reason she doesn't do anything about it is because she knows he can do so much better. She clearly wants to be to Jimmy what Chuck has failed on all accounts to be - someone to depend on.
Well, I say get away with murder as a catchy turn of phrase.
Jimmy has a flair for presentation. I don't know whether it's because he's charming so he can make any situation sound good or that he makes any situation sound good is what makes him charming. But if you say it in sheer literal terms: "Jimmy committed a crime" then there's no getting away with it. But Jimmy wouldn't say that. He'd frame it as helping his associate and friend, making a tiny alteration to the documents, one that is almost meaningless, and easy to fix, with no great loss done to anyone.
A good example is actually the opening scene of the show. That's Jimmy working his hardest to present the situation in as best a light as possible. Everything Jimmy says is perfectly true, but he skirts around addressing what the 3 boys actually did. They were in the thralls of youth, having a good time, something they won't do again, and it was a victimless crime wherein no body got hurt. It's a very convincing defense all things considered. As a counter, the prosecuter says absolutely nothing and simply shows the jury the court tape. There is no attention paid to presentation, neither condemnation or scorn: The prosecutor just shows it like it is: The boys had sex with a head. And just like that, Jimmy lost.
So when I say that Jimmy gets away with murder, it's not that people wouldn't hold him accountable if they had the stark truth of what he does. But he paints everything in the best possible light when he absolutely has to tell the truth, and most of the time, it works. Back when he was working for Davis and Main, Chuck immediately spotted that Jimmy solicited his clients, which he did. But Jimmy worded his explanation in such a way that it was innocent. But if Chuck had evidence of the stark truth, davis and main would be far less satisfied. That may be the biggest contrast with the two brothers. Jimmy tries to distort reality to make it fit his version as much as he wants, but Chuck's skills as a lawyer revolve around citing factual evidence in support of his case. The closest he came to distortion is his rhetorical false assurances that Kim has everything covered to Mesa Verde which itself is designed around layering the amount of factual issues that Kim would have to contend with to serve them, and then he then immediately defaults to simply presenting more factual evidence ("Kim is just one person, we as a firm can handle your needs better).
That said, I think Chuck exasperates this effect. While people like Jimmy, that rarely clouds their vision of him to the extent that his likability is the only reason he can do anything. In his betrayal speech, he cites his likability as the only real reason that Jimmy can be a lawyer, when Jimmy actually worked quite hard doing real (if occasionally unorthodox) detective/lawyer work. The reason the Sandpiper case exists isn't because Jimmy slicked anyone, it's because he noticed a deficiency in the numbers while working a smaller case, found a legal loophole in which to obtain the documents he needed, then reconstructed them (with chuck's help), making a damn federal case. That is authentic lawyer work that chuck tries to ignore. Meanwhile, people actually
do like Chuck. He's highly respected and revered. Howard treats him right and defers to him when he is uncertain. Jimmy worships the guy, and takes care of him out of a genuine love even despite all that happened to him. Even Ernie doesn't seem to have an issue with Chuck until he goes ballistic with his crusade. He had a wife that was genuinely fond of him. His issue is less that he is unloved (by the characters within the show anyway. Some people in this thread would mount his head on a pike in front of his burning house.) and more that he
feels unloved.
The scene with his mother dying is specially key. There is absolutely no reason to believe that either parent favored Jimmy. That his mom said Jimmy twice before immediately dying could have happened for literally any reason at all. It doesn't mean she loved Jimmy more. That Chuck interprets it that way regardless is more of a statement on his psychology than direct evidence of his parents regard.