Hi All, I'm going to have 4-5 days on my backpacking trip that I can spend in either The Black Forest (Freiburg and probably Baden Baden) or Austria (Salzburg & Innsbruck). Which one is a better choice for a 22 year old on her first backpacking trip???
(Oh, and Vienna is out because it's too far off my path)

That is a really difficult question to answer. What do you enjoy? Tell us a bit more about yourself?
I have been to both and they are both great.
I might lean towards salzburg and Innsbruck. You can experience the larger town/city environmnet(Museums, Churches, tours, ie: The sound Of Music Tour...which by the way I loved!) and if you like to hike you have access to beautiful mountain hiking outside both towns.
have a great time where ever you go, bith are wonderful!!!

Well, no matter which place I choose, I will definitely be doing some hiking. Museums and such are always a plus because I'm an artist...but not mandatory for this leg because I'll be getting my fill in Berlin, Paris, & Munich.

The hiking will be more dramatic in the Salzburg/Innsbruck area because there you have the alps and the mountains in the Black Forest are not high. OTOH, there is still plenty of excellent hiking in the BF region, as well as picturesque towns. Re museums, aside from the museums in the BF itself, you are a short train ride from Basel, Switzerland, which has several interesting museums.
Freiburg is a university town, so you will run into more people in your own age group. Baden-Baden tends to attract older visitors in most restaurants/hotels/cafes you will see people in the 30s, 40s, and older (although not everywhere...some places, like Amadeus on Leopoldsplatz draw in the 20 somethings).