King Jackie won 53% of his games, Mullen has won 57%. What is 'obvious' about 4%? Played 11 games back in King Jackie's day, most likely all 4 would have been patsies. But, just for comparison, let's give him 3 wins out of 4, just like Mullen. Then his winning percentage is 55%. He also tied Arkansas and Arkansas State. In modern times you'd play that out in OT, so let's assume a split there. Still 55%. So you've got a 2% difference. Technically you are correct.
NOW....let's take it a bit further. Both King Jackie and Mullen went 3-1 vs. Ole Miss in their first 4 years. King Jackie's best wins during that stretch:
@ Texas '92 (6-5)
Florida '92 (9-4, SEC East Champs)
Tennessee '94 (8-4)
@ South Carolina '94 (7-5)
Mullen's best wins:
Ole Miss '09 (9-4)
Georgia '10 (6-7)
Florida '10 (8-5)
Michigan '10 (7-6)
You could argue a few others, like Kentucky '09 which was 7-6, but I think Georgia trumps that, simply because it was our first victory over them in forever.
So, looking at those two bodies of work, I wouldn't say Mullen is "obviously" better than King Jackie. Mullen has been more consistent and doesn't lose to terrible teams, but King Jackie beat better teams.