I love the M3 more in just about every category than the S4, save for the interior, but have doubts about its winter handling. I do not want to have 2 cars to be responsible for, but plowing is an option with a company truck, though I would really like to stay away from plowing if at all possible. So is it worth it to buy the M3 and try to drive it in the snow? Should I plow? Or should I just cross to the darkside and go for the S4?

if you get "winter tires" (fka "snow tires") the m3 will be fine in the snow. I run Dunlop Winter Sports thru the snow filled alleys of Chicago without a problem.

had both cars before. The m3 wins hands down in performance and value. The s4 is a car that grows on you. It's handling is okay, could be better, but it shines when the weather is nasty outside. I had a 2001 s4 that was totaled in an accident, then i purchased a 2001 m3. With good snow tires, the m3 will do fine in the snow, but if you want to blast down the road and don't care about anything in the snow-the s4 is the selection you should go with.

go for the snow tires

M3 with snow tires works well but not at well as S4.

I run snow tires in winters but you would need to be gentle in the snow...M3 just has tons of power under the hood.