Many have said that vanagons do have poor traction. I had a diesel converted to
gas and it was not very good even with snows. The pre vanagon buses are better
as they have greater weight in the rear (fuel tank and batteries back there). I
have also driven vanagon syncros and Eurovans (non syncro)

My rating is this:

Best to worst - Vanagon syncro (any tire), Eurovan w/4 snows, 75 bus w/2 snows,
Vanagon (any tire)

Camper/non campers make little difference as the extra weight is pretty much
added equal front to rear.
The EV seems to be so good (at least with snows) cause it has so much weight
over the driving wheels.  Seems to be a far greater proportion then vanagons.

I have never had a bus with 4 snows but I suspect that this may be even better
then the EV with 4 snows.