Just as an illustration, if you run firecalc on standard settings for 30 years, 85% equities and ask it to investigate for 50% failure rate (the average), you'll end up with:
6% withdrawal rate.
The 100% success rate is 3.59% withdrawal rate, about half (a bit more) than the 6%.
VPW would start with the 6% and advise you to shift downwards to the 3.59% when things don't go well (or upwards otherwise).
The biggest thing VPW seems to do is thus start from the typical scenario vs. start from the worst scenario.
6% withdrawal rate.
The 100% success rate is 3.59% withdrawal rate, about half (a bit more) than the 6%.
VPW would start with the 6% and advise you to shift downwards to the 3.59% when things don't go well (or upwards otherwise).
The biggest thing VPW seems to do is thus start from the typical scenario vs. start from the worst scenario.