Military law/punishments are a unique system. There are many factors that go into determining a sentence for a particular accused. You do have the maximum that can be imposed, though that's rarely done. Oftentimes you have a person negotiating a pretrial agreement, wherein they plead guilty to a certain offense in trade for a cap on the amount of confinement, reduction in rank, amount of fine, type of discharge, that can be imposed by either the judge or jury. There are no minimum sentence requirements, such as seen in many state/federal courts. In determining a "fair" sentence, some of the things that are looked at is what the offense is, what sentences have been imposed for that type of offense previously, what's been upheld on appeal/review, the track record of the accused, the aggravating and mitigating circumstances at the time the offense occurred, the amount of remorse "shown" by the accused, etc.
With respect to officer vs enlisted status and preferential treatment, I've seen officers nailed as severe as the enlisted, and sometimes harsher. It does, in part, depend on who's sitting in the command seat at the time and the standard to which they hold the officers responsible.
