How's the overworld in Mafia 3? The one in 2 felt really tacked on, selling stolen cars and robbing stores was pointless since you lost all your money during several points in the story, and all you could buy were guns that you were already given for missions. Granted the first Mafia didn't have much to do outside of the main storyline either except for those side missions the mechanic gives you, they were still a lot more memorable than anything in 2.
Vavra doesn't speak about what happened during the Mafia 2 development but my guess is he wanted to make something big and ambitious, maybe overly so (what with KCD being in its fifth year of development and counting), whereas 2K aimed more or less for a quick-ish and inexpensive cash grab based on a somewhat popular IP.
Not sure what was better. If Vavra stayed and was given a creative control we'd have probably got a much bigger, complex, memorable and expensive game. But with the GTA series hoovering up the market it's uncertain if 2K could recover the ballooned investment. Maybe the market is not big enough for two giant IPs.
Therefore I'm pretty certain Mafia 3 won't even try to be a GTA killer. Just something cheap and quick to capitalize on a popular genre.