Summary Hearings deal with minor or disciplinary offences and are normally held by your Commanding Officer. You do though have the right to elect for a trial by Court Martial regardless of the seriousness of the charge. You also have the right to appeal the decision made by your Commanding Officer to the Summary Appeal Court.
Legal representation is only available for a Court Martial but the sentence you could receive cannot be any greater than that available to your Commanding Officer. If you agree to a Summary Hearing you can appeal to the Summary Appeal Court in which case you will be entitled to legal representation.
Bearing in mind the consequences that any charge against you has on your career, seeking early legal advice to help you consider your options is essential.