Consider equal sized Roth and Trad IRA accounts. Over longer spans of time, stocks are expected to grow faster than bonds. So if the stocks go in Trad IRA, you expect to have a larger balance than if you put bonds in Trad IRA. You only owe tax on the Trad IRA, not the Roth IRA. So placing bonds in the Trad IRA, with slower expected growth, should result in paying less tax.
When comparing taxable v.s. Trad IRA, you need to consider the time frame. The article referenced earlier mentions the tradeoff: in taxable the stock dividends result in tax each year. But cashing in the gains can be done at a lower tax rate. Over short periods stocks do better in taxable than Trad IRA. Over longer periods, deferring tax on stock dividends tilts the balance towards Trad IRA.
forummm - You ignored (C), taxable non-retirement.