I have not owned both, but when I decided to sell my LP12, I considered the Classic III. I was fortunate enough to happen upon a dealer that had one on display with he same cartridge as I had. Also they had McIntosh Pre and amplifier hooked up. I have a Mc amp and I thought I would get a good comparison. In short the VPI was such a departure from what I was used too, I ended up buying a Rega RP10, as it was much closer to what I had grown to love about the LP12. So I guess a short answer would be, two different tables in many ways and therefore the sound is quite different as well.
All my own opinion of course
All my own opinion of course