Same here on the verify thing. With all the DVD's I've burned, I've never once used the verify option. Never could see much point in doing it (other than for the sake of just doing it because I can), especially when the verify takes as long as the original burn. I just play it. It something is wrong in that area (which is very rare), I just burn it again.
As far as the Imgburn vs VSO thing. Reading this forum, you will see all sorts of people having one burning problem or another with the VSO engine. Dunno what's up with it really. Look again for similar issues with Imgburn. You won't see any or very few (and of those, I'd say most would be more on the user error side rather than program problems).
As long as I've had DVDFab, I think I've only used it's VSO burning engine once. I've been an Imgburn guy since it came out and before that burned with DVD Decrypter (which is made by the same person) so I just have no need for the DVDFab built in burn function. It's a preference thing and of course it would have to be trouble free or I wouldn't still be using it.
For me, one of the best things Fengtao did was when he incorporated the Imgburn option into DVDFab. That was a really good move.