I have to agree with momofboiler1 … I would choose Northwestern over WashU. As you pointed out, camjlara41, Northwestern and WashU are similar in many ways, so it would be helpful to eliminate one of the two, to help you really focus on comparing / contrasting that university to the university you are most familiar and comfortable with, UCLA.
It is also very helpful that all 3 universities are similar in price. It is crazy that both NW and WashU are cheaper than your in state UCLA!
Given who you are and what you have described, my vote for you is:
1)Northwestern
2)UCLA
3)WashU
Good luck with your decision. All 3 are obviously world class universities so be confident that whichever you choose, you will be exposed to wonderful opportunities!