and where, my dear, are you getting all these assumptions? do you go to columbia? or are you basing this on what sally said that bobby said that his cousin said his best friend said about columbia? it's been one semester in, and i'm pretty sure i don't have a knife sticking out of my back. as for competitive--well, this is dental school. i really don't see a difference between the competitiveness of columbia dental and my major during undergrad.
to the OP, predents really can't give you a definite answer as to which school is the best, etc--they don't go to both schools, how in the hell are they supposed to compare the two? i would suggesting pm-ing current columbia and ucsf students, asking them what they think the pros/cons of their school are, and then think it over.