The Washington Department of Transportation was asked to test snow tires vs. studded snow tires. The test was performed on an ice-skating rink. At that time, Blizzak snow tires manufactured by Bridgestone tire company were used. The Blizzak tires stopped better and the vehicles cornered better than the best studded snow tires. That is the reason state highway patrol cars are equipped with nonstudded snow tires.
It is a mystery why this information was not given to the general public. The problem with studded tires is that they do not have enough studs per tire and after a few miles the studs become rounded on the ends, losing even more traction.