I've been using the Shimano boots for the last two winters and even in last years extreme temps I was pretty toasty (most of the time). Use them mostly on the road but have done me proud on the few off road rides I've used them for.
Mine are the original version which have a stretchy entry which can be a pain but I think they've changed that to a velcro strap now.
I'm made up with 'em but the NW Celcius/Fahrenheit look just as good.
Chances are non of them are gonna keep your feet dry as the water is gonna get in by your ankle. Being gortex, the general idea is to keep the cold wind out so you're feet stay warm even when wet.