"I've bet on every Cubs game so far...they've been heavy favorites in each one"

If you bet on baseball regularly, you gotta go with the underdog because if you look at the record of the best and worse teams at the end of the year, there is not the disparity you'd see in football or basketball. Especially if you go with strongly favored teams, you might have to win 2 out of 3 games just to break even.