I strongly agree with other posters here, if you were to actually be able to visit WASHU, I think you would put it ahead of NU. It is really one of the most beautiful campuses in the nation. Socially it is amazing - with something for everyone. The only thing missing is D1 sports. Look at the campus, Loop area and Forest Park via google maps if you are unable to visit. Look into their med-prep program if at all thinking of pre-med. Google the medical school admission rates for WASHU graduates. It is easy to double major or switch majors and many students graduate with a double major and a minor.
UCLA and NU are also amazing - every school has pros/cons. You will have to prioritize what those are for yourself but ultimately any of the 3 are winners. Congratulations!