On the long run into retirement I used to use the Financials Engine tool available through the Vanguard site but these days I prefer the FRIP and FIRECALC calculators.
FIRECALC and *****, using historical data, definitely provide more optimistic scenarios. I always liked FRIP because of the "underperforming market"/90% confidence option (although as noted above the 95% confidence level has been removed).
Now I don't know what to think as the new results show only the tax bracket one is assumed to be in, while the former version showed exact yearly amounts of estimated taxes to be paid, without any mention of a tax bracket. So to me comparing results from the old to the new version is like comparing apples and oranges. Worst, the former version showed me paying some taxes (albeit low), and now I'm assumed to be in a "0" tax bracket, which makes no sense. When I use the tax calculator provided, I'm given a 9% federal/2% state (CA) tax bracket, which isn't useful because it fails to take into account taxable accounts/roths, etc.