Is there an independent tire rating site where I can compare all these tires I'm considering?  I've found different people saying the same tire is both excellent and crap in snow.  

The mud and snow rating on tires are a little deceptive. Snow is a tricky terrain to choose a tire for. There really is no accurate chart. When you say snow do you mean fresh snow or packed? Wet or dry? Will there be on-road ice involved? If road ice is involved you'll likely want to steer clear of mud tires and look for something with plenty of sipes in the tread. If no ice, then go for a mud type tire. What tires are you considering?