Should I Learn Russian or German?

I had to make the same decision as an undergraduate. I chose German because Germany was simply a country I was more interested in, as well as the fact that probably 3/4 of my ancestors are German (the rest English and Scottish, so no Slavic ancestry at all).

Recently, however, I've become more interested in the Slavic languages. I think in general (for political science, which I majored in with Linguistics, and I now have a master's in International Relations) it's going to be entirely a personal decision. In learning languages, I have found it easier to learn a more difficult language first (German before attempting Spanish). Others on this forum have sternly disagreed with me (I suggested to someone learn Ancient Greek before Latin and took a lot of heat for it).

You're leaning towards Russian, I say go with that instinct. German is a very useful language, younger generations speak English with relative fluency but they absolutely appreciate you attempting German. Russian still leaves a bitter taste in the mouths of many in Central and Eastern Europe, but many will speak it (my German friends from Saxony and Saxony-Anhalt started learning Russian before English).

Learn Russian first. It's much more challenging and you'll enjoy speaking it in general! Yes, many Germans speak great English. But Russians not so much. More of a reason to learn Russian first!