I saw this a while back and have been meaning to post on it:
I've generally used the higher volume stuff as a means to lose weight or for general cardiovascular fitness. Also it's pretty good for injury prevention as long as the exercises are varied. I've pretty much been in that mode on and off for a few years now. Having said i'm also at my most muscular now that I probably ever have been and as close to the maximum predicted muscle weight as i'm likely to get, so it's not been bad for size either.
For myself higher volume has generally been 30 sets three times a week. Or more recently 30 sets four times a week for a total of 120 sets a week. Something like 24 sets per bodypart per week. Variety of exercises/sets/reps is very high, otherwise I burn out quickly on that type of volume.
When i'm at my strongest training is very specific toward the type of strength I want to show (rep range, lifts etc) so I generally have a much narrower focus of exercises.