> would let you effectively contribute more (if you want to) because you are contributing with after-tax money

This is really the wrong way to think about this (basically, what you're saying is at best technically true).

1. You're ignoring the tax savings from contributing to a Traditional that result in more income which can then be invested, used to pay down debt, etc. Only if you spend it on ephemeral stuff does that money "disappear".

2. The goal with the "Roth vs. Traditional" decision should really be made based on whatever nets you the most money to spend in retirement. For most high earners, that's almost certainly Traditional. Read Roth or Traditional for a longer discussion.

(tagging /u/hankmoody666)