Ok, so, i checked out and tried both amps at once, here are the results on MY opinion:
Tried with a 2x12 loaded with celestions v30. On the clean settings, the VHT sounded nice, lots of headroom, but thing is, it sounded a little too "stiff" and not the classic clean which I really like. The Mark III has a wonderful clean, open, warm, very very fenderish.
On the crunch, I liked a little bit the R2 of the mark III, very marshallish.
And the lead, the most important: I have heard that the VHT was a dry amp, but I wasn´t really prepared for this kind of dryness. Couldn´t found my favourites lead tones with this amp no matter what, maybe it was because the lack of Graphic EQ, I really don´t know, but for heavy tight rythm the channel is quite good. The Mark III is the complete opposite: big sounding, tight but NOT overly tight creamy and liquid leads, the notes just pop out of the fretboard, didn´t have the need to play as hard on my strings, and the rythm tone is way more aggresive. The gain on those two was about the same amount, just the dryness of the VHT seemed like there was a little less (the MKIII is known for the gain achievement).
For me, there was no contest, the guy even offered me the trade without the Yammy, which tempted me a LOT, but prices aside, for my applications, the Mark III GS all day long.
Both amps were good at low volumes I must say, but I decided to keep my Mark III GS and in the future get another type of amp, possibly a EVH 5153.
Thanks again and just writing to comment my impressions.