Similarities:
Generally speaking, both will follow the base base structure and have the same objective, which is to persuade people into thinking differently or, more precisely, into thinking about a subjecti in the way that you want them to.
Differences:
Clearly, one of them is written and one of them is spoken.
While in an essay, you have to pay attention to written structure and grammar in many ways, in a speech, you have to pay attention to your body language, positioning and even voice tone.