An optional essay is always “optional,” so if you have the opportunity to showcase yourself further on your application--DO IT! It can be a valuable and additive component to your application; however, you must use it to your advantage in the right way.
Many optional essays are open-ended, asking you to include anything additional that you believe the admissions committee should know about you. Some ask specific questions that, if relevant to you, should be addressed. For example, you may be asked about your relocation plan if you are choosing a part-time MBA that is far from where you live currently. If it applies to you, then answer it. In these cases, the optional essay is really only “semi” optional.
In general, keep the following in mind when approaching the optional essay, especially for open-ended cases: