I mean yeah, you're correct, but once you get into retirement tax rates everything pretty much a crap shoot. I simply wanted to look at overall account balances as I would tend to assume that when a person has a balance of X dollars, they will be withdrawing that at roughly the same rate whether the money is in in the MBCBP or not. As I said any withdrawals from the non-MBCBP would be taxed at long-term capital gains rates, which theoretically would be lower than the earned income rates of the MBCBP. But with the non-MBCBP you're also paying some taxes each year if your personal portfolio has turnover or earns dividends. In a broad sense that probably comes close to washing out the difference between that and the income taxes you'd pay on the MBCBP withdrawals, hence why I just stuck to a basic look at overall account balance as a comparison.

In the end there's just a whole ton of personal variables that each one of us will have in retirement that will have huge affects on our tax situation and how much each person needs to draw down each year from their various accounts. Roth accounts vs traditional, real estate income, military or other pensions, a working spouse, etc.