not for some petty reason like money or prestige, but for the satisfaction that I would get from knowing that I made a difference in someone's life.
This part is not very strong, because it tells the reader something different than what you intend it to tell. It tells that you have money and prestige on your mind, and it wastes time with a cliche about "making a difference."
I think you should do some more reading. Read some great memoirs of physicians. Read the work of someone whose specialization appeals to you. THEN, you will have some fresh ideas and insights in mind, and they will be reflected in the essay.
Think about what this says about you: provides outstanding medical education but it also shortens the overall period of study...
Be strategic, and use words that instill in the reader a sense of inspiration. Get specific with your philosophy of medicine and intentions for the future. :-)