Is Shearling That Much Warmer Than The Equivalent Thickness Fleece?

[AtlantaSpike]

My cheap (but real shearling) B-3 knockoff has been the greatest cold weather MC jacket I've ever owned. I don't find it too hot when it's not absolutely frigid like most here, but maybe that's just me. It just seems to do a much better job than fleece or any of the technical jackets I own of keeping the wind out and your body temp in.