A 3 Essay does the following:

It is, Generally effective, focused, has a clear relationship between ideas, it demonstrates adequate completeness, mostly contributes, it is smoothed, and controlled, and there is minimum wordkiness; development of ideas is prevalent, and is thoughtful, sustains connections, and mostly authentic/original.

A 4 Essay does the following

Focused, ideas are completely related to each other, there is a sense of completeness and meaningfulness, mostly contributes, smooth/controlled, contains meaningful transitions, it enhances ideas, development of ideas is thoughtful/specific/insightful, unique, compositional risks are rampant, develops a relationship with audience, and most of all, utilizes syntax and literary devices (anaphora, polysyndeton, asyndeton etc...) to contribute to the essay in an insightful and meaningful manner.