I compromise, just call me indecisive and wimpy. Most of the time I wear some old style Shimano winter boots (all leather uppers with a lace keeper strap. Every fall I coat them with more water "proofing". They are a size larger than I usually wear so there is room for heavier wool socks or thin socks & seal skinz as the weather suggests. They have SPD cleats, that take a fair amount of maintenence in winter salt conditions. I seal the unsused holes in the sole with silicon caulk. I pulled the original insoles, which were the same thickness as my summer shoes, and replaced them with thick felt ones. For pedals I use Shimano 323/324's. That lets me clip in on good days, clip only 1 foot, or turn the pedal and use the platform side. That system is good down to about 5F/-15C. Below that I just wear my Sorels. While they are warmer, they are heavy, clumsy and prone to sliding off the pedal at critical moments. I find it very hard to pedal smoothly in them. My personal cut-off point for snow depth is 6inches/14 cm. My route is too dark and too full of SUV's with drivers that don't understand that the best way to drive in snow is to slow down and go at a constant speed. They prefer to fishtail across the road.