Never ridden either, but one difference ss'ers seem to fret about is that the brake tries to spit the axle out of the back of the non drive side dropout on horizontal dropout/track-ended disc frames. Unless you put the disc mount inside the rear triangle like the newer on one scandal and horizontal dropout inbred. (and another frame which escapes me right now).
The wanga is clunkier looking than the genesis, but gets the best of both worlds as it has screws to push the dropouts back like trackends but the whole dropout moves (no need to reset the disc brake when you change ratios or the chain wears) and the dropouts are vertical so the axle stays put under heavy braking.
If it was my money I would save a few pennies more and get a 'new-shape' scandal, or get a brand new inbred and spend the change on some posh chain tugs.