Thanks. I should have been more specific. I have no company match, so that's a non-issue, unfortunately.
Good point on deductions. The past two years I've itemized deductions, as I rent out my second bedroom and have costs associated with that, but I got married this year and truly have zero idea what my tax situation will be this year.
Sounds like it's one vote for taxable investments. I could always mix and match, a bit, of course, and throw a couple extra hundred towards my mortgage or HELOC, but the bulk to Vanguard.