In today's world it's is more than the 4-wheel drive system and more than the tires themselves; it's the vehicle.
Think back on your driving history. My first car was an MG. Even with snow tires it was the worst. Once it even got stuck on level, hard packed snow. In grad school I owned a Datsun 510, a poor man's BMW. Had to have "the look" and installed wide tires. School in Utah in the winter with those tires was not a good choice, but that car got around just fine. The IRS perhaps? My VW was excellent in snow as was the reward I bought for myself, a new Carrera, but those had the help of rear weight. The Explorer AWD V8 was excellent with Michelin LTX M/S and much better than my XC90 which has the OEM all seasons - soon to be replaced with something better. My wife drives to work in a commuter car, a front wheel drive Focus with all season tires. Absolutely horrible in snow of any depth.
The point, of course, is, it's much more than the tires or the 4- wheel drive system and don't ask me why - it just is. We all know cars that are excellent in snow but not necessarily why. So look at the total package, don't go wide on the tires and if you drive half the year in a snow filled environment use dedicated snow tires for the snow period. It's my belief all 4-wheel drive systems today are pretty good, pretty quick to engage and will meet your requirements. It's the vehicle dynamics and let's not forget the driver - a very big influence.