There’s only a small window between crossing into the 25% tax bracket and getting phased out from making a deductible tIRA contribution. At that point I think the Roth is the better choice again.

It will never make any sense for high income earners who fail to qualify for the tax breaks to invest in a IRA. If you convert a IRA with no deductions to a Roth IRA you just paid double income tax on your money. Paying 33%+ (depends on the high income bracket) then paying another 33%+ makes no sense. At that point you're paying the government more taxes than just long term capital gains tax and not receiving the investment returns of the 33% over X amount of years.