Ride all winter -
- Good for the engine if you get it up to full operating temperature. That requires probably at least 20 minutes of riding time. Otherwise you risk condensation in the engine and exhaust and that ain't good!
- Bad for the general exterior of the bike if the roads have salt and brine residue on them. The corrosive effect is strong, unless you do a thorough cleaning of the bike.
- Good to keep skills intact. I found when I rode year around I didn't have any sort of "lag" in skills when spring came around and I rode more.
- Bad for a new rider when it comes to road conditions. Salt, brine, and any other sort of deicing debris can cause traction issues. Unless the road is clear and washed clean by rain or melting snow you risk possibly dumping the bike on the crappy surface.
- Good to ride right up until the road conditions are bad, because the bike does get run. The engine has a thermostat just like a car to get the engine up to operating temps. Blocking the radiator usually isn't needed on a road bike, although I have had to do it on the dual sport due to the large amount of radiator cooling for the slow off road capability.