Herbert and VH4....
I am not so sure why the VH4 is labeled as ONLY good for rock and the Herbert is labeled ONLY good for metal. Both amps can really do anything. I was in the studio and the producer said within a couple of minutes that to his ears the Herbert was the best sounding clean he has heard. I was surprised such a statement was made so fast but he has been in the game for almost 40 years so he knows what he likes.
I have found brutal metal tones and liquid leads along with shimmering cleans on the Herbert. I have found the same on the VH4. IMO, the VH4 works incredibly well for heavy downstrokes. It has a crisp, articulate punch to it that is both massive and clear and I love the low end of that amp. The right cabinets really help these amps shine even more. A decent cab doesn't make either sound bad but the right cab makes each sound that much better.
Regarding the Herbert, it has been said before that it can get lost in the mix and that it doesn't cut. I don't believe that to be true, certainly not IME. I guess any amp will not cut if you max the gain and bass and zero out the mids...lol. The more I play both amps, the more I love them. I think my favorite (barely) is the VH4. Not to mention, the Einstein is an incredible amp as well. I also feel the VH4 needs to be worked while the Herbert is (easier) to play. Neither are difficult to play however if you are sloppy, the Herbert is more forgiving IMO, then the VH4.
Here are my thoughts regarding the two broken down...
PM Riffage- VH4
Alternate picking heavy stuff - Herbert
Violin Leads - Herbert
Chords that ring, Notes that breathe - VH4
Cleans - Both
Jazzy stuff - VH4
AC/DC style rock - VH4 channel 2
Running them in Stereo - Heaven
Just my $.02