I think the largest factor in traction is the tires. What ever you choose, go for dedicated snow tires. That will allow what ever system (2WD, 4WD, AWD) to make the most of the traction available.
If you have concerns of ice, I would get them studded. The studs are noisy, but worth it on icy conditions.
Make sure you do all 4 tires! Some still just want to do the main drive wheels. That is fine, unless you plan on stopping and turning at some point. If you have AWD or 4WD, you absolutely must do all 4, as the AWD/4WD will be "expecting" it.
Yes, there is an upfront cost (snow tires and summer tires). However, the miles you save on your summer tires will help offset that cost. Also, when snow tires get to worn, I pull the studs out and run them through the summer until they are done. I get about 90k to 100k miles (out of a set of snow tires and a set of the stock Michelin tires) on my truck with this method.
I am a huge fan of Hakkapeliitta snow tires. They are from Nokia (yes, the cell phone people). In short, they are high performance snow tires, designed and built in Finland (and they know a thing or two about snow).
Nokian Hakkapeliitta 5
Also, in the past few years many others tire companies have taken notice of the high performance snow tires, and started to make some affordable and fairly decent copies. These are usually knock offs of an older Gislaved or Hakkapeliitta design, but they often work well for cheap. The one I like from this category is the General Artic Altimax.
General Altimax Arctic
Bridgestone makes a tire called the Blizzak. It is a stud less ice tire. They are OK. The bad news is they wear fast, and once you are through the first 50% of the tread they are kind of useless. I have tried a set, and went back to Hakkapeliitta tires.