Quoted from vireland:
GB Premium destroys the Pro. Subway ramp is way better, magna slings are cool, Slimer does more than just bounce up and down in the same place, Ecto goggles are neat, Library and storage unit are not just a crappy flat plastic. It's a much better experience.
That said, I'd recommend the mezel mods cover for the Firehouse HQ. It looks a WHOLE lot better:
I agree with Vireland, the Premium model on GB in my opinion is worth the extra money. The pro is also a good game as well but the extras on the Premium are pretty sweet, and yes the magna sling rock! If you love your GB and plan on keeping it and can afford the extra coin, i would upgrade to the Premium.