Is the personal statement that big of a deal, or could they care less?
It’s a very selective school. No doubt your competition will submit the optional essay. Yes, do the personal statement.
I did, but mine was only about a paragraph. I got accepted, but I think they really value quantitative data over qualitative information. I’d say it really depends on the rest of your application, especially your test scores and GPA.
The essay is the only thing that separates you from 40-- or 400-- other kids with exactly the same statistics. Absolutely do it, and do it thoughtfully.