If we had a country that was conservative enough to repeal the 16th amendment, we's also be able to easily privatize social security, reform medicare, and reduce welfare. And under those circumstances, with the government cut in half, then we would be able to have the discussion about whether an income tax or a sales tax is better. We do not have that country, and the 16th repeal is not going to happen after a sales tax is implemented.
"we would be able to have the discussion about whether an income tax or a sales tax is better"
You seem to not realize that that very "discussion" is being held right now and is in fact very far along.
... and the income tax is not the one "winning". The FairTax is - in fact it has already won. The only question remaining is how soon will it be voted into law. It is clearly the better system economically AND the one needed to move the country ahead economically on a number of fronts. Many economic studies show this.