Stock market returns an average annual return of 8-10% with dividends reinvested. This is over the long term.

That said, I would want to pay off debt at 6%. It's not 20% debt, but still debt nonetheless.

I don't think you need to make extra payments on your mortgage assuming you refinanced around 3%. Take the extra money you were putting on your mortgage payments and put it on the 6% debt. Keep investing in your Roth 401k and investment account.