Yes they are very much an upgrade from the VSD1. There's no contest. The bass alone is vastly superior to the VSD1, and the highs aren't as prone to sibilance as the VSD1. The VSD1 might do detail slightly better because of their more sharper highs, but the mids are much more lush and vibrant, and instrument separation is another win for the Piston.
Thanks for the answer, would you say the pistons are 'fun' and bassy headphones?