Joe:
I think the problem with USB turntables is that you don't get much choice about the quality of the turntable, pickup and cartridge. Doing it with separates isn't inherently better, but it does give you the option of choosing a really good record player component.

Hamish:
Pedantic clarification: Audacity doesn't have a "free version", it is free software. It saves stuff in its own project format that enables editing info like labels, multiple tracks etc. to be saved with the project. It also exports to lots of other formats including WAV and MP3.

Some Linux versions of Audacity are supplied without the MP3 encoder library, but that's because the MP3 library code is always available as a separate package as it's used by lots of other prpograms.