@mamaedefamilia brought up another great point - Dartmouth is definitely more rural and WashU is more urban. Another nice thing about WashU is how close the airport is (20 min) - I don’t know if these things are important to you but they were to my D.
My D picked WashU because of its high collaborative atmosphere, the students are very nice and not competitive with each other, laid back, lots of restaurants, stunningly/beautiful campus, southern hospitality, loved the dorms (including the fact they were coed), offers study abroad in Florence with her class and professors, her major had some neat and unusual aspects to it, urban setting (was very important to her), close proximity to the airport, warmer climate, etc. Those are the small things that are important to her so you should decide what’s important to you. That will help you pick the place where you’d like to be at for the next 4 years.
Let me give you an example of what she didn’t like - there were colleges on her list that was in a rural setting, 2 hours from a major airport, had curfews where the opposite sex had to leave at midnight during the week and 2am on the weekends, super cold weather in the winters, heavy drinking/drugs, etc.
You are right to be concerned about Dartmouth’s greek life. Take a look at this… http://www.huffingtonpost.com/2015/01/29/dartmouth-ban-liquor-drinking-reform_n_6567940.html