The difference is that crimes such as disorderly conduct are subjective not just for police, but also for juries. It's not perfect, but twelve people agree that you were causing trouble at a level that rises to criminality, there's a good chance there's something to it. With open container laws, it's only subjective for the police. Once you're charged, then all they have to prove about your conduct is that you had an open drink, not the real reason they decided to go after you.
Yes, but the jury will be asked to decide the question of whether the accused had an open container, of which there will be little doubt.
A jury could decide that it's a case of selective malicious prosecution and acquit the accused despite believing them to have committed the crime, but that's uncommon and a much bigger reach than a jury weighing whether the accused was engaged in disorderly conduct because they're charged with disorderly conduct.
