More grip on the studded tires than in the tarmac stages.
Related, but still kinda off topic, I recently learned that the Sno*Drift Rally in Michigan is one of the toughest rallies anywhere because Michigan doesn't allow metal studded tires on public roads, therefore the rally cars can't be fitted with them either.
Not too sure that they get better grip than they do with semi-slicks on warm/dry tarmac, but definitely better grip than they do on
gravel.
Yes, the above is why Team McKenna did so poorly this year in that rally with his 'hybrid' Fiesta open class car, which is an older FIA S2000 class Fiesta roller with an '08 Focus WRC M-Sport 2.0 liter turbo engine transplanted into it.
The original S2000 class cars had naturally aspirated 2.0 liter, high revving powerplants, but had great AWD/sequential drivetrains in them.
He had NO GRIP at all, but still managed to place third against the
very well funded, and equipped 'works' (Vermont Sportscar/Lance Smith prepped) Scoobies, which did a much better job at 'tractionizing' <-(look it up) their spike-less Yokohama snow/ice tires, than Barry McKenna did to his Pirelli equivalents.