Converting now reduces your balance in traditional IRAs, so it reduces future RMDs. By less being required to be distributed as RMDs, more of your traditional IRA funds can end up as Roth conversions if you choose to continue to do Roth conversions after RMDs begin. For the same tax liability, reducing your RMD by some amount allows an amount equal to that reduction to be converted to Roth instead of being moved to a taxable account.
