Though I am not ready to admit that I attend one of the two said schools in this discussion --- Let me tell you a little bit about NU.
In your position, the perspective on which school is better may be skewed... Ultimately, finding and matching in a field and place that makes you happy is paramount.
You are predominantly in the classroom during the first 2 years. NU has prepared it's students very well during the preclinical years. Average board scores have been 235+ for the last 3 years. Many competitive residencies (and even away rotations) cut off applications at some level, 230s and 240s will at least get you through the first door. Additionally, we are moving towards progressively earlier clinical experiences.
2) you may not appreciate the quality of clinical facilities and instruction yet, but...Northwestern Memorial Hospital is ranked #12 in the nation. It is clean, well kept, and fairly "efficient" in it's operations. The campus also includes a brand new Children's Hospital, relatively new women's hospital (<10 years), and a new outpatient tower that is going up as you are pondering these merits. Additionally, NU is home to almost all the major divisions/departments that exist in medicine. If you want exposure or research in things like CT surgery, neurosurgery, plastic surgery, dermatology, interventional radiology, inpatient psychiatry, etc etc -- NU is definitely a place that offers these experiences to jr and sr students.
3) Many NU students end up staying at NU for residency. There is a reason for this, Chicago is a wonderful city (and we are nestled in the safest part of it) and the programs are fun, instructional, and non malignant. The faculty are for the most part -- academicians and enjoy research and teaching.