I just moved, and the internet has not been turned on yet at my home, but yes, the SJ fabric is at least 3-4x thicker. Maybe it's because they use different materials/fabrics, but the VS tent's material is thin and flimsy compared to the thick and sturdy material of the SJ. If the SJ tent's material is 210D now, it would be ridiculous to make it 400D or 800D IMHO... If I had internet at home, I would have uploaded a video to youtube for you. It should be turned on by Monday morning if you want to wait until then. Basically, the SJ tent is really nice, solid, and again study..
I ordered the SJ tent on Amazon, but while I was waiting for it to be delivered, I came across (seen it being used in a youtube video) and ordered the VS tent which was cheaper. I opened and used the VS tent first and was happy with it until I decided to keep and open the SJ tent. I then realized the difference in overall build quality and features, and started to be annoyed a little by the VS tent... Don't get me wrong, the VS tent was okay, but it was like being happy with eating at Red Lobster and later finding a 4 star restaurant that didn't cost much more.. You become aware of how much better the food could/should be... I use the VS tent for veg and the SJ tent for flowering.
Long story short... If you want a decent tent at a steal of a price that will should work just fine, get the VS. If you want a better tent with excellent build quality and design, get the SJ or Gorilla. I have not used the Gorilla tent, but I hear it's a good buy, but just overpriced. To me, I got the best of both worlds with the SJ tent... The price was in between the VS and Gorilla tent, and the quality was great...
I suggest that if money is an issue, get the VS tent. If you got the extra cash to throw around, get the Gorilla tent. If you want something that's up to par quality wise, but isn't as expensive as the Gorilla tent, get the SJ. Either way, all 3 tents should do what they were designed to do...