Global,

The you are right about tax rates now and later in your logic. What you are forgetting is that your investments should grow.

So let's assume your tax rate does go down in retirement like you are assuming. Let's say your average tax rate in your earning years is 30% and it goes down to 25% in retirement. Let's say you save $1million during your working years at your 30% tax rate. That $1million grows to $2million by the time you start taking distributions in retirement at your new 25% tax rate. Would you rather pay 30% on your $1million now or 25% on your 2 million later? That is the argument for Roth.

"Tax the seed not the harvest" as another poster said.