This is an extremely important question and one which causes a lot of trepidation amongst my clients who elect to go to trial. One of the advantages of a negotiated outcome is that you take the "unknown wildcard" out of the equation. The wildcard is the judge and the unknown is the sentence he or she will impose based upon a guilty verdict returned by the jury.
If you go to trial and the jury returns a guilty verdict, the judge is free to impose any lawful sentence. That means for a 1st offense OUI, you can be looking at anything from a simple fine and license suspension, all the way up to 364 days jail. While the chances of being incarcerated for such a lengthy time is slim to none, the possibility of jail is real and a frightening one at that.
For example, if you have a BrAC of .15% or greater and the jury finds you are guilty on the aggravated OUI charge, you will be going to jail. The question is for how long. The answer isn't an easy one. Each judge has their own nuances and tendencies and it's important that your attorney be familiar with those sentencing tendencies so the client can make an informed decision on whether to elect a jury trial or enter into a plea negotiation.
I've been on the receiving end of a guilty verdict when defending a client and to put it frankly, it's no fun. It's no fun for me because of all the time I've invested in defending the case and it's even worse for the client who has to now live with a conviction and possible jail time. The only way to have a certain outcome is either A) get the case dismissed following a successful motion to suppress hearing or B) negotiate an outcome that hopefully doesn't equate to an OUI conviction.
ALL the best lawyers lose at trial eventually. The ones that say they don't are either lying or haven't tried many cases. If you want certainty, trial may not be the right answer in your paricular case.