I don't know of any quality difference; I'm not the person
to ask. VC papers first became popular with students, as I
recall, because overall it's cheaper than buying 2-3 grades
of the same paper. It also works well because students are
often less likely to get a properly exposed negative that
prints adequately on a specific grade. But VC has has other
creative possibilites and also became popular for that.

I use graded mainly because I don't have creative issues
with negative exposure/densities (unless of course I make
a mistake.) Also, I don't like dealing with the filters and
my older cold light doesn't accommodate VC anyway. All my
negatives are exposed and developed so as to print on a
specific grade of paper with a full tonal range; I rarely
need go to a different grade. I also have little need for
print controls via splitting contrast grades in the same
print. I consider that a sign of faulty craft (i.e., not
knowing how to get a properly exposed negative.) Ideally,
if you know how to obtain a good negative through exposure
and development that will print with both good shadow and
highlight detail on a certain paper grade, you also know
how you'll be printing that negative when you make it. If
fine tuning is necessary I prefer to use other available
printing controls.

On the other hand maybe I'm just an old fart who isn't keen
on changing his ways :)

I'll be interested in Tom's reply too. Never the less the thing I would
say about graded paper is that the graded papers I have seen (Forte)
have  much more consistent plots emulsion to emulsion than VC papers for
a given grade. There is some leeway between grades before one becomes
the higher or the lower adjacent grade.