17% DC on $44k earnings over the IRS 415c income threshold would cover the catch up contribution amount for those who want a traditional account. I wouldn't say the MBCBP is a better retirement vehicle than a Roth catch up, but is a good way to minimize the negative impact of spill cash for those over 50 who plan on catch up contributions. There are still plenty of reasons for using Roth over traditional if your goal is maximizing retirement funding.

Lost in all of the Roth, traditional, 415C, MBCBP, catchup, back door math is the real question. I think sometimes we are overly focused on maximizing vs optimizing the tax and growth equation. What is your goal for retirement funding?

You may end up with millions, but not be able to spend it. I'm in the process of segmenting my bucket list into age categories. For example I doubt I'll be up for rafting through the Grand Canyon when I'm 70, so it's better for me to skip the catch up this year and do the rafting trip. If the goal is a two week European river cruise, save away and cruise at 70.