compared to a non-studded tire, marathon winters are slow. however, my set of marathon winters (700x35) are faster than my old schwalbe snow studs (26x1.90) that i ran on my old mountain bike. the 26" version of the snow studs were fairly knobby and geared more towards snow than ice. the marathon winters are much smoother, though with enough tread to get me through 95% of what i deal with during a typical chicago winter.

for a studded tire, i've found my marathon winters to be decently fast-rolling (because they're not particularly knobby).

the thing that really slows all studded tires down is the fact that you have to lower the pressure if you want the studs to do their job. rolling studded tires at 90psi will not give you nearly as much traction on black ice as rolling them at 45psi.