I too have wondering as to how much of an influence using the Superbias routine has over just a simple MasterBias. Like you, I have been too lazy to do any quantitative analysis
Just did similar to what you did, just got:
Master Bias: ~2.25
SuperBias: ~1.25
When I subtracted the Master Bias from SuperBias I ended up with a SD of ~4. If I did it without adding a pedestal and ended with 4.645 ADU average.