Being an Alaskan, I own both Sorels and Bunnie Boots, as well as a few other brands.
Sorels, are good for light outdoor use, chores around the house, outdoor events that keep you moving, etc... Anything below zero degrees and they are left behind.
Bunnie boots, are what most of us call tennis shoes or slippers. They are toastie warm and I never wear anything more than a regular sock or thin wool socks. At first they are awkward to walk in, but with time they are like any other foot wear. I wear them all day long for ice fishing, work, and anything that requires long periods of time in the cold. If they do get wet, all you do is dump the water out and put them back on, the heavy insulation will keep your feet warm even if wet. You do need to look for the real deal though, I think Beta or Batam as mentioned above are the knock off brands and will not perform the same. One last thing About bunnies is make sure you get the white ones, as the black version is not rated for -60
Another brand to look at for quality cold weather boot with a different soul are Baffins. They are rated from -60 to -148 farenheight. They are standard issue for Pruhdoe Bay