Age. 3/4 years difference in NFL experience
Role in the offense. Goff was asked to be the Rams offense this year and turned in a 4th best passing, 7th overall offense even with all of the issues at RB and OL. Garoppolo was not asked to be the focus of his offense, nor was he the primary target to stop.
8 man fronts - SF faced 8 man fronts significantly (more than 10% of the time) more often than the Rams did.
