I am going to be a senior soon and I’m unsure whether I want to apply to restrictive early action to Princeton or early decision to Columbia. I love Columbia’s environment in the big city, but I also like Princeton’s focus on undergrads. I’m having trouble figuring out of environment or prestige is more important. I want to major in political science and later go to law school, so what would be the better college for someone like me?
The one that accepts you.
If you need to compare FA offers, SCEA to Princeton. Columbia’s ED acceptance rate is higher than Princeton’s SCEA acceptance rate, but it may even out when recruited athletes, legacies, etc are backed out. Columbia’s Core is more restrictive than Princeton’s gen ed requirements, but some people like the Core. Princeton requires a thesis, while Columbia does not.
Columbia has a much better Law school (ranked 5), compared to Princeton whose rank I couldn’t find. (Princeton’s political science is ranked three but Columbia’s close behind ranked 7).
I think that Columbia would be a better choice for you. It is still very prestigious and although Princeton may be ranked number one overall Columbia sounds better your specific major. Also, you seem to really like the environment. Apply to both to keep your choices open but I suggest applying to Columbia early decision.
Best of luck! 
Sources for ranking-
https://www.usnews.com/best-graduate-schools/top-law-schools/law-rankings
https://www.usnews.com/best-graduate-schools/top-humanities-schools/political-science-rankings
Grad school / professional school rankings have no bearing on undergraduate education, IMO. Regardless, the grad rankings are close enough to be statistically insignificant.
And Princeton has no law school.
With respect to prestige, you haven’t defined the order. Which of these schools do you regard as more prestigious?
I often hear that Princeton is more prestigious.
“Columbia has a much better Law school (ranked 5), compared to Princeton whose rank I couldn’t find.”
Of course you “couldn’t find” Princeton’s law school ranking since Princeton doesn’t have one. Princeton also doesn’t have the rest of the popular triumvirate schools, Business and Medical.
I think the choice, based on your core stated criteria, should be between the school in the ultimate urban environment (Columbia) and the school with the greater emphasis on undergraduates (Princeton). With sincere reflection, the right decision should become clear to you.
For play, you can search “Top Lawyer Producer Schools – Infographic.”
Both schools should be prestigious enough for anyone. Pick the one that is the best fit for you. Consider things like location curriculum etc.
Based on the limited information you provided, Columbia ED would be the best choice for you.
Look at class sizes and availability of classes (meaning, is it hard to get into the classes you want). Know that prestige and ranking are useful only very broadly but the difference between #2 and #5, for example, is meaningless. For IR, you should also consider Georgetown University.
Both schools are a fine choice for pre-law. Have you visited both? Princeton is a sleepy little town, and Columbia is right in the middle of one of the biggest cities in the world. They couldn’t be more different in terms of vibe. Pick wherever you think you’d be happiest for the next 4 years. Getting into either is a great accomplishment.
Even the most stellar applicants non-hooked are usually rejected from those universities. Just apply to the one you like more.