I just saw this post and had to admire Vinnie's articulate comment about Mark's singing.
I click the video link and the first comment I see:

Raises an interesting discussion point.

Whilst I admire Robert's work on the first album, I prefer Mark's voice on All Systems Go.

That said, there's not much to choose between their voices. I'd love to understand exactly what VV has a problem with, with regards to Mark's vocals.

Vinnie just has a lot of unresolved hate for poor Mark. Nobody can understand it, it's childish and pointless.

Look how bad it makes him look and he posted it willingly himself.