"A pair of 5:10's and a pair or really grippy pedals such as Eastons Flatboys, Burgtecs or Straightlines are a whole different ball game to vans/DC/Skate shoes. I use them for DH and you have to physically lift your foot to reposition it, you can't just wiggle it about."
That's true, but it's also meaningless as a test. Nobody doubts whether 5 10s have more grip, they definately do, the question is whether the Vans have enough. I own both but I tend to wear my Vans, they're just nicer shoes and don't soak up water as enthusiastically. I guess if I was dhwnhilling I'd want more but the only time the Vans ever lack grip is if I unweight them, and the 5 10s will slip then as well.
I had the same epiphany all 5 10s wearers do- I stuck my foot on the pedal and it felt amazing, tried to squirm my foot around, it was stuck! It was only later that I really thought about the difference on the trail and found there wasn't much.
(incidentally, the best Vans sole for mtb use isn't the waffle at all IMO, it's the older round tread sole, but it's pretty much died out)