Bracken_Joy -
Differences I know of with Roth 401K vs. Roth IRA:
1. Roth 401K - no income limits. Roth IRA - has income limits which are easily circumvented via the Backdoor Roth technique. So pretty much the same if you're organized.
2. Roth 401K - up to 18K (24K if over 50) contributions. Roth IRA - 5.5K (6.5K), although since you can do both at the same time this isn't really a difference of consequence.
3. Roth 401K - early withdrawal is pro-rated between basis and earnings, so you're likely to get hit with penalties and some tax on earnings if you withdraw early. There are some exceptions, of course.
Roth IRA - Early Withdrawal is subject to ordering rules. These ordering rules are what allow us to say "withdraw contributions at any time, tax and penalty free".
This is an advantage to the Roth IRA, although not a huge one, plus it is easily worked around most of the time - just roll the Roth 401K over to a Roth IRA, and the contributions follow.
4. Roth 401K - subject to RMDs. Roth IRA - no RMDs. Again, the "fix" is to just roll the Roth 401K over to the Roth IRA.
5. Roth 401K - investment choices are what your employer offers. Roth IRA - choices are more or less unlimited. This can go either way - if you have a good Roth 401K at a sufficiently large employer, odds are you can get lower-cost investments than you can find on your own. A bad 401K may be a reason to favor a taxable account over the Roth 401K, whereas the tax-savings on the traditional 401K require the 401K to be even worse for that to be the situation. But then you have to factor in that the 401K, Roth or Traditional isn't forever and you can't make up for missed years. So the plan has to be pretty bad. And this is a criticism of the specific 401K - not of Roth 401Ks as a whole.
I don't know, I guess I'm not seeing from any of that "Roth 401K is almost universally a bad move" The main reason the people on this forum are likely to be better served by Traditional is the intersection of high tax rates today (we skew relatively high income) with lower tax rates on withdrawal (we also skew towards lower post-retirement spending and income than pre-retirement income). But certainly there are exceptions - for example, if your taxable income is so low that you're in the 0% tax bracket, Roth is the obvious play, 401K or IRA as the case may be. Or you have a remarkably low income year compared to a typical accumulation-phase year for you.
Another possible source of confusion - in a 401K, there is such a thing as after-tax contributions which are not the same thing as Roth contributions. Until fairly recently, these went largely unused, because of the way they work if you leave them in the 401K and eventually withdraw from there. You save no tax today - like a Roth 401K. Growth is tax-deferred - like a Roth 401K. But you pay ordinary income rates when you eventually withdraw - very much not like a Roth 401K - you pay no tax on qualified withdrawals from a Roth 401K. But the IRS in a stunning move in 2014 or thereabouts, sent out a clarifying memo giving the OK for the MEGABackdoor Roth IRA technique (
http://www.madfientist.com/after-tax-contributions/). Now after-tax (Not Roth) contributions have a much more valid use-case, and there is therefore much more discussion around them. I know I used to mentally equate after-tax with Roth, but in a 401K, and with knowledge of the MEGA backdoor Roth, that is an incomplete way of looking at things.
