My previous winter tires, the original 1st generation Michellin X-Ice, finally needed to be replaced after 9 seasons of use (around 22,000 miles). I liked their performance in nasty winter conditions, as well as dry and wet conditions. After watching/reading Tire Rack's test results and looking at numerous other sources, I decided to go with the Michellin X-Ice Xi3 tires.
I'm reviewing this tire mounted on a 1999 BMW 540i 6-speed manual with approx. 650 miles driven on the set. The performance is great! They grab really well while accelerating and braking in light snow (about as well as my summer tires do in wet/rainy conditions). In deeper packed snow, they provide noticeably better traction than the 1st generation X-Ice tires. Even when they are driven beyond their traction capabilities on packed snow, they provide a predictable response making it rather easy to correct the loss of traction and regain control.
Compared to a the set of Continental WinterForce tires on my 2008 BMW 535Xi, I would say that these provide more traction, especially on icy and packed-snow roads. It is a little hard to differentiate the tires abilities since the 535Xi is all-wheel drive, but when braking (which doesn't make use of the all-wheel drive), the X-Ice Xi3 performs better in every condition. The Continental is still a great tire, and I would recommend it if you want a more comfortable and quieter ride, and are willing to sacrifice a little snow/ice traction and dry/wet road handling to get it. They are still very capable and I have never been stuck in the Continentals, but the Michellin X-Ice Xi3 just provide a little extra traction, along with better dry/wet road handling and a sense of confidence when driving in winter weather.
If you have an all-wheel drive vehicle, both the Continental and Michellin will work well. However, if you drive a rear-wheel drive vehicle, I would highly recommend the Michellin X-Ice Xi3 for it's added bite in winter weather conditions.