That’s a tricky question.
Nothing I have on the system provides constant on-screen monitoring of both CPUs - I have a temp. indicator, which usually tells me that CPU 0 runs hotter than CPU 1, indicating heavier usage, and Windows Task Manager provides a graph-type display of both CPUs, but neither tell me whether its software or O/S overhead usage on the second core, and neither provides a work-load percentage difference between the cores.
As I said, it’s never been mentioned in any of the releases, so I’m not sure if DVDFab has been optimised for multi-core systems, and with limited monitoring capabilities, I can’t give you a definitive answer - maybe one of the more tech-oriented members will read this and offer a better answer than I can give you.
There should be a speed increase, but of unknown magnitude by me at this point.