If I wanted to use one tool to merge and convert vobs to an mpeg file, I would use Vob2Mpg, not this new tool which requires two steps.
I could also use VobMerge first, before using this new tool, but that is two steps again.
The only thing going for this new tool, DVDVob2Mpg, is the fact that it seems to work with no issues in Windows 8.
Vob files by themselves are rarely useful as individual pieces of a dvd-video. They are arbitrarily split into 1gb divisions within the movie, and therefore it doesn't make sense to try to work with them as separate files.