It's improved in practically every area. It's faster, smoother, flashier, features far more playable characters (20 in all), allows more enemies on-screen at once, and covers much more of the story from the anime and comic. Only place it's kind of dropped in quality is the graphics, but that drop in graphical quality is exactly what makes some of the improvements possible.
Don't judge the book by its cover on this one. They've really done a lot to tweak and improve it. Playing the demo and watching a few videos actually is enough to tell in this case.