Once I've maxed my employee match, should I invest more into my Roth 401k or Roth IRA?

The Roth IRA. Shorter term, there are situations where you can pull out contributions and earnings (http://www.schwab.com/public/schwab/investing/retirement_and_planning/understanding_iras/roth_ira/withdrawal_rules) without paying taxes. Longer term, there are no Required Minimum Distributions (RMDs) during your lifetime with Roth IRAs. This makes them a great way to pass on wealth. With a 401(k) (either Traditional or Roth), you have to do something with the money every year starting at age 70.5 (http://www.irs.gov/Retirement-Plans/Plan-Participant,-Employee/Retirement-Topics---Required-Minimum-Distributions-(RMDs).

Congratulations on maxing out your employer match - that's the first step in financial success - taking advantage of opportunities presented. There really aren't many differences between a Roth 401(k) and a Roth IRA...both are after-tax investments on your part.  While I know you can withdraw your Roth IRA contributions after 5-years, tax-free, I'm not sure how that works in a 401(k) plan...my guess is the same, but if you think you may need to access these funds in the intermediate term, I'd look into that before deciding. Best of luck.