Filthstep is the lo-fi, Super Nintendo cousin of Dubstep. It’s somewhere between Nerdcore and Seattle garage band music. It sounds like a 5th generation copy of a cassette tape half the time. That’s one part of the “filth” term.
Wobblestep focuses on the wobble aspect of Dubstep. The wobble is the heavy synthesizer bass line with smooth pitch bends that drives the low-end of the frequency spectrum. Here, it’s accentuated and placed up front.