To add to this --- I used the complete 'DVDFab' download for a couple of years now and I know it comes packaged up with the VSO burn engine, although the VSO engine is not from the authors of DVDFab.
From a user point, it does look like it is I guess and the DVDFab software works seamslessly with the VSO engine, i.e. nothing extra shows on screen when the burn starts except the entries in the log.
I used the VSO engine for 90% of my backups and think this works really well (always using good media of course) but for me I ran into a few problems a couple of DVDFab releases ago (cannot remember which now), where the burn to disc did not work.
It wasn't a huge issue in that I could do the back-ups again but I wasted about 5 discs and took me a little time to figure the problem.
As a net result I tried the ImgBurn engine and whilst this too works seamlessly, you know when the burn starts not only from the log but also as ImgBurn starts in a new window of it's own.
For me and looking at all ImgBurn has to offer there are lots more parameters and tweaks you can make for the burns and control the drives etc..., so for now I'll be sticking to that.
This all said and tools in the toolbox, VSO has served me well I will of course update this and as future versions of DVDFab come out may use this again but for the moment ImgBurn does the job.