Answer:
There are no best words to use when writing an essay, it all depends on the context, grade level, goal, and energy. If an essay is meant to be formal or serious, don't use slang, and refrain from adding comedic jokes. On the other hand, if you're trying to give off a more homey, welcoming aura, you should use happier words that will make your essay emit a more positive tone.
Hope this helps, and good luck with your essay :)