Nothing really
Career- you are forced to start off with a small school, you can create a coach from scratch, milestones
Open- you can choose any small school or power conf team(you still can work your way up to a power) freedom to edit any team, player or coach(ratings also; only before you start a legacy is when you caj change your coach ratings) you want, can watch or play any game outside of your schedule, coaching changes are still there; you cant create a coach, milestones(for legacy points) are gone..