Let me start with I am not expert. I spent a lot of time plugging in numbers to a spreadsheet (yes I built one) trying to solve this question. I am over 50. The bottom line was for normal rates of return 7-13% there was not that much difference between the two investment option in terms of what you get after taxes down the road. Most of the time the Roth 401k gave more per year but in the low hundred maybe as much as $250 dollars more.

Now there are a couple points that make that true. For the two plans to be similar, you must be investing the tax savings back into the plan. For example, if your tax savings on 23K is 8K, you must invest that 8K back into your 401k as after tax savings. If you do not invest the tax savings, then the Roth 401k kills and there is no comparison. The Roth will crush the traditional 401k.

The deciding factor for me was the fact that I don't have mandatory withdrawals from the Roth 401k like I will with the traditional 401k. That means hopefully, I never have to withdraw that money and it's there for my wife later down the road.