I had a really hard time cutting down my Pitt essay to 250 words, but once I finally did, it was a better written and more concise piece. Look at every phrase in every sentence and ask yourself: is this saying something new? do i need to say this to make my point?
I think erring on the side of fewer words than the max, whenever humanly possible, is a good way to go. These poor guys have a lot of reading to do, and every couple sentences extra is that much more potential boredom for them (no offense to you or your writing, personally 🙂 ). My mentor was on an adcom and he says that short and sweet is key.
Good luck with Pitt... it's a wonderful, wonderful place. I couldn't have been more impressed with it!