Herges. Reason being he's more secure as closer, despite his unsatisfactory overall numbers. Plus, Herges at least gives a sliver of hope that he can right the ship, as the guy has been a reasonably effective pitcher for several years.
Betancourt is almost sure to lose the job back to Riske, just a matter "when" rather than "if". He throws everything at about the same speed, and his fastball flattens out too often.