Ugg-type boot (or EMUs) with the genuine Shearling lining - will keep your feet warm.
Since they may most likely be suede exterior - they will not keep your feet dry (for long).
You may wear Uggs/Emus on dry crisp days or snowy days that are so cold that the snow will not melt. If you're in the city, the snow will melt b/c of salt/sand treatments.
You're better off getting either a leather boot exterior that's been Shearling lined - or some other sort of really warm lining -
OR
you can get sheepskin exterior or maybe even suede exterior - as long as it has been fully treated by the manufacturer and definitely waterproof/weatherproof.
B4 i bought my La Canadienne boot (see above) i bought an awesome pair of boots from Town shoes and from Aldo - they had great grips, were genuine leather and were lined with a synthetic extra warm lining. To keep your feet warmer, you can get a shearling insole as well. i've tried Sorel (synthetic) boots - and they leaked! Ditto for all other synthetic boots i bought before.