I'm not expecting this to be popular but the two big scooters I've had have been brilliant for winter..
fairing keeps the cold off and the crap away from the bike innards (the downside is having to get panels off to do maintenance, luckily it doesn't need much)
they are low enough so you can balance, the tyres give you plenty of warning so you should be able to stop a slide before it starts as long as your taking your time (and not going down a massive hill in 2ft of snow following a tractor tyre trail..)
There is something to be said for a bike that does everything, but there isn't really any such thing.
(This winter is the first winter I've not been using the bike to commute the whole time, since the nhs are paying for fuel and parking for a car then I'm borrowing one to get to the hospital, but not for uni. Allot of its convenience but also really could do without turning up in an ambulance, needing an xray and potential future colleagues seeing my balls)