Who should I start this week? Matt Ryan or Phillp Rivers?

Matt Ryan just cam off a great Performance against the Saints in a win and has to face the Niners next at home who haven't been stopping the p. Phillip Rivers had 455 yards last week in a loss to Seattle and is at home facing the Cardinals who got smoked 41-7 by Matt Ryan and the Falcons in WK 2. So I ask, who should get the start?