@DrGoogle ,
The way I see it, the Roth conversion decision is tax-driven. You have to understand your different tax rates when each decision is being made and make projections as to how the scenario will pay out. Again, this is the task for a good Excel-spreadsheet and tax-competent person. The questions I would ask are:
(1) what is the marginal tax rate if conversion is done from tIRA to rIRA
(2) project income from all sources (DI, QDI, LTCG distributions), pensions, SS are various stages of post-work years and then add in your age 70.5+ RMDs: what is your likely effective tax rate then
(3) do you believe you will NEED any of your RMDs or will they be saved and invested (after paying OI tax on them) into taxable accounts
– my ILs did this as a continuation of a lifetime of frugality. Those accounts were then inherited and the new owners got the step-up in basis upon their passing.
(4) do you think that your estate will grow to such a size as to become taxable for Federal and state tax purposes
– you’d have to compare the difference between paying OI tax to convert vs. paying your effective estate tax rate on the taxable part of your estate
(5) do you think you’ll leave the IRA to your kids or grandkids
– might they actually have lower marginal tax rates than you have while taking the RMDs
– if they end up getting the inherited IRA while in their 40s for kids or 20s for grandkids, this is something to consider
(6) if you do “pre-pay” your OI taxes to convert from tIRA to rIRA, then you’ll have a Roth and will not be required to take RMDs for your lifetime or your surviving spouse’s lifetime (if he/she makes it his/her own)
You can see from these questions that it is a personal decision for which one answer will not fit all.
And, then, there is legislative risk that the laws governing IRAs and Roths may change.