I would say the other two would be a tie, very similar curriculums (with 2 yrs of medical school). UConn would slightly be more competitive than Columbia - due to it's smaller class size (40).
Columbia has the higher avg DAT scores, while PENN has the higher incoming cum/sci gpa's. CONN is in the middle on both but will rarely let in out-of-staters, making it most difficult for non-conn applicants. All 3 are great schools and you can't go wrong with either.
try to raise your GPA (3.5 and above) before the next cycle... and you will be set. The schools you are interested will look at your science GPA very closely.