You are better off with an ACD than with a violation. The ACD seals itself by operation of law, but even until it does seal it is on your record as a dismissal. The violation is for less than a crime (it's neither a misdemeanor
nor a felony) but it does involve a plea of guilty. So it is a conviction and will be on your record as such. Yes, it would be appealable because it is a plea, but you would still need a lawful basis to appeal it.
In other words, you can't appeal the ACD because the case would be dismissed. You can appeal the violation, but only if there's a legal reason entitling you to appeal it.
In point of fact, it is almost impossible to get a negotiated plea back once you have agreed to it and been sentenced to it. So if you don't think you are going to like the plea, don't take it in the first place. The law doesn't allow you to agree just to get the benefit of the bargain without you being willing to really hold up your side of the deal too. And if that's what you think you are going to try to do, you'll be disappointed in the results.
A violation can be sealed if the court agrees to do that for you but it is not as tight a seal as the ACD. That is, NYS law allows for a violation to be unsealed and inspected under far more circumstances than they would allow an ACD to be opened.