Self employed

Okay, for the sake of calculation, let me put it this way.

If I pay 20% federal tax of $25,000, it's $5,000.

Say I add this amount to my estimated income of $30,000, for example.  Now, it's $55,000.

As I pay the federal tax upfront, the actual amount to convert to Roth IRA is $20,000.

Then, my total estimated income is $50,000, which puts me in the 12% federal tax bracket.

Here, my tax is $6,000 ($50,000 divided by 0.12).  But as I have paid $2,000 upfront in federal taxes,

the total taxes I would pay would be $8,000.

Now, let me withhold the federal tax and add the whole contribution ($25,000) to my estimated income.

It's now $55,000, which puts me in the 12% federal tax bracket.

So, 12% of $55,000 (assuming I withhold the federal tax) is $6,600.

In other words, $8,000 vs $6,600, to put it simply. Withholding is more beneficial to me, isn't it?

Am I right or wrong?