Greetings! Between a 401(k) option and the pension fund, sounds like a sweet gig.
More details may be required on fund offerings within the 401(k) plan, as well as approximate tax bracket. Shedding taxable income into your 401(k) is always a good thing, but if the funds choices are poor with high expense ratios and your tax bracket is reasonably low, a taxable investment account with Vanguard might be a better option.
I haven't used Betterment, but have been extremely happy with Vanguard for both taxable and retirement accounts.
Good luck!