My daughter was accepted to both and attended Southwestern.
Both are great schools. Southwestern is smaller.
My D entered Southwestern with a bunch of AP/dual enrollment credit. She studied abroad twice-one summer and one semester, did a summer REU at Norte Dame U, and graduated in 3-1/2years. She completed an Econ major and her minor was only two courses short of a second major. She landed a dream job in her field of study when she graduated, and is currently working on a PhD. She also met some great friends there and Georgetown is a nice little town. She had a great experience at Southwestern.
Both schools are majority Texans but my daughter is not from Texas had friends from other states and at least one foreign country.