Border Collie
You will find this video useful. It conclusively demonstrates winter tyres are better than 4x4 in the snow.
http://www.youtube.com/watch?v=7l2cMlNRX_A
However, the best would be to have both if money allows.
My ideal "compromise" would be to have 4x4 and Goodyear Vector4seasons all weather tyres. This will save the hassle of changing tyres every 6 months and have very decent performance in all conditions all year round and not just on snow.
I would not buy from a main dealer anymore because they won't or can't come close to internet prices. I bought my last MPV on the net and saved about £3.5K, so well worth doing. In my case Arnold Clarke and it was actually a very pleasant experience. There is very low risk buying online (more likely by phone).
Hope that helps.