It depends on the environment you seek. Some students want a big university where they can get lost in the crowd and meet new people every day, where sports matter a lot, etc. Some students want small, discussion-based classes and few friends they know well. Their choices with regards to Oxford-Emory vs. Emory University will reflect that - not their test scores or accomplishments.
It makes no difference in the end: regardless of what campus you choose, you are admitted to Emory and you graduate from Emory.