That doesn't seem obviously true to me? The manner in which a crime is committed affects all stages of the legal process, including sentencing, jury deliberati

That doesn't seem obviously true to me? The manner in which a crime is committed affects all stages of the legal process, including sentencing, jury deliberation, and those considerations will certainly also affect how a prosecutor decides to charge someone. If you're saying that someone hiring a hitman has the exact same probability distribution of getting charged (let's say, given airtight evidence in both cases) compared to someone who pulls the trigger, that seems like a very strong and surprising claim. If you're saying that 'in theory' both crimes would rate a certain type of murder charge, that sounds reasonable. Even then though, the prosecutor would certainly be able to tack on other charges (e.g. assault with a deadly weapon) that tangibly affect the outcome, from plea bargaining onwards. And that seems correct? One of the goals of the criminal justice system is to prevent future crime, so to the extent that the manner a crime is committed reveals information about the future threat level of a criminal, society (and by extension, the legal system) should take that into account.