Tbh, I am more inclined to SMU.
SMU's pedagogy forces you to speak out more. When you do that repeatedly over the course of 4 years, quite a fair bit of transformation takes place. They say that you can easily identify an SMU student from a crowd.
That is not an exaggeration. When I interview prospect, I can generally tell which ones are from SMU. That said, NUS is a very reputable school as well. Ultimately your outcome depends on how much effort you yourself put in when going through your 4 years of education as well.