I don't know anything about the other calculators you've used, but FIRECalc gives you a pretty good dose of history. The "problem" is that if you retire in your early 40s and live for 50+ years then FIRECalc doesn't have as much data to work with.
If you really want to tweak all the retirement-planning parameters then you could sign up for a membership with FinancialEngines.com, or pay for ESPlanner, or try ORP, or read Otar's PDF. If you can't find failure among that bunch of fairly credible calculators then you're good to go.
The book written on E-R.org, "The Military Guide to Financial Independence and Retirement", on sale now! For more info see "About Me" in my profile.
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