I downloaded Mafia II Definitive Edition and holy crap, it's several times the size of the original, 64-bit, uses (slower) D3D11 renderer instead of D3D9 one, loading times are longer, physics effects are a bit glitchy, stutters a bit, even on consoles, positional audio seems inaccurate in places, its benchmark detects my CPU frequency being whooping 10000 GHz. It crashed before I got control in the chapter 2, I guess it ran out of RAM.
There's a sharper texture there and there, some new option there and there in menus, some removed, tweaked lightning, but it's not some radical overhaul of the original, yet still so much bigger. In the folder with the executable, there are literally dozens of redundant DLLs, even 32-bit ones. You can delete all but 3 of them.