A 700 is a strong score, and it will not negatively impact your application. However, you should understand that on your application your GMAT score is self-reported, and you will record your highest score. Admissions teams will focus on your highest score, and because of this there isn't a downside to taking the test again if you feel you can greatly improve your score.
This being said you do have a strong score, and if you have to choose between spending time studying or working on other areas of your application, I recommend the latter.
Here is school specific advice for Columbia and Duke:
Duke: http://www.stacyblackman.com/category/d ... ua-advice/
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MBA blogger, US News and Author, The MBA Application Roadmap